Skip to main content

Full text of "Leavening agents; yeast, leaven, salt-rising fermentation, baking powder, aerated bread, milk powder"

See other formats


Published by 

The Chemical Publishing Co. 

Easton, Penna. 
Publishers of Scientific Books 

Engineering Chemistry Portland Cement 

Agricultural Chemistry Qualitative Analysis 

Household Chemistry Chemists' Pocket Manual 

Metallurgy, Etc. 



Yeast, Leaven, Salt-Rising Fermentation, 

Baking Powder, Aerated Bread, 

Milk Powder 










This volume fills a gap in the literature of baking in this 
country. The baker knows a good deal about his flours and 
also how they are made, but he knows very little about his yeast 
and less still about his baking powder. He has been well sup- 
plied with literature on the technology and chemistry of flour, 
but much of the data on his aerating agents has either been 
aimed over his head or else has been purposely misleading. 

Aerated bread has been added because of its historical value 
and because of its possible future. Dry Milk is another recent 
important addition to baking materials. 

Yeast, which is necessarily a technical subject, has been treated 
in as condensed and simple a manner as possible. The author 
acknowledges his indebtedness to an anonymous friend for the 
section on the manufacture of yeast. This is the first exact and 
detailed description of yeast manufacture in English, and is an 
important addition to the literature of chemical technology. 

Baking powder is a subject on which the bakers and the public 
have been misinformed. The water has been so badly stirred 
up by the "baking powder controversy," that the non-technical 
man has been unable to see beyond the words "alum" and "cream 
of tartar." This section has been written without personal 
bias and the facts have been verified. 

The author also wishes to express his thanks for the data and 
valuable criticisms given him by Dr. Edward Hart, the librarians 
of the John Crerar Library of Chicago, Meek-Barnes Baking 
Co., of Los Angeles, Lewis C. Merrell and Charles Trefzger, 
and to acknowledge the assistance of his friends. 

R. N. HART. 
Peoria, 111., Aug. 1914. 



Fermentation and Its Cause I 

I/if e and Characteristics of Yeast 3 

Activities of Yeast Breathing, Nutrition, Fermentation 8 

Selection Hansen's Pure Culture 15 

Keeping of Yeast 16 

Tests for Yeast 20 

Manufacture of Compressed Yeast 21 

Old Vienna Process Materials, Disturbances in Fermentation 25 

Aeration Process Materials, Disturbances in Fermentation 33 

Yeast in Bread 36 

Leaven and Homemade Yeasts 43 



General 5 i 

The Alkali 53 

The Acid Cream of Tarter, Phosphate, Aluminum Salts . - 54 

Starch 5 8 

General 5 8 

Kind of Flour 60 

Care of Baking Powders 60 

Miscellaneous Substitutes 61 

Residues in the Bread 62 

Manufacture 63 

Analysis 64 

General 67 




/The study of yeast falls under three heads : ( i ) Briefly, the 
discovery of the source and nature of alcoholic fermentation, and 
a growing knowledge of what yeast is; 1 (2) the characteristics 
of the yeast plant; (3) yeast manufacture and use. To this 
is added (4) the action of yeast in bread and (5) Leaven- and 
homemade yeasts. 


Fermentation has always been an interesting and puzzling sub- 
ject to the physical scientist. The alchemists of old hoped to 
bring about a fermentation of the base metals to produce gold 
and silver; the "philosopher's stone" would induce this fer- 
mentation. Yeast, of course, is as old as fermentation. But 
fermentation, until 100 years ago, was thought to be a chemical 
reaction. For instance, Basil Valentine, a German Monk of the 
fifteenth century, held with others that it was a purification of 
the must, by which the true nature of the alcohol appeared, and 
the excrement or baser substances settled as lees. When yeast 
was added to wort "an internal inflammation is communicated 
to the liquid, so that it raised itself, and thus the segregation 
and separation of the feculant .from the clear, takes place." 

Leeuwenhoeck opened the book of yeast in 1680, when he 
discovered the beer yeast globules, by means of his improved 
microscope; but it did not occur to him that the cells were 
alive, de Latour, Schwann and Kuetzing turned the first page, 
with the discovery of a vegetable mass of cells that reproduced 
by budding. In 1838 Meyer created the yeast genus Saccha- 

1 For an excellent treatise on "Fermentation" see Encyclopedia 
Brittanica, 1911; Vol. X, p. 275: also "American Handy Book of Brew- 
ing, Malting and Auxiliary Trades," Wahl and Henius, Chicago, 1908. 


romyces of the fungi; because it was now known that yeast 
breathed oxygen and excreted fermentation products, without 
secreting chlorophyll (leaf green). In 1870 Dr. Max Rees 
narrowed the term yeast to those cells which broke up sugar 
into alcohol, excluding all other bacteria and fungi which pro- 
duced fermentation. 

Taken in detail the history of fermentation research is seen 
to include the names of the most illustrious chemists since the 
foundation of chemistry. Liebig, whose deductions were of less 
importance than the controversy he started, threw the immense 
weight of his influence in favor of the hypothesis that fermen- 
tation was a chemical reaction. He entered this field of research 
about 1838 and was not successfully challenged until Pasteur 
published his "fhude sur la Biere" in 1876. Pasteur's work 
compelled Liebig to modify his own views somewhat. In later 
years Pasteur's work has been amplified and amended by Traube, 
Buchner and A. J. Brown. 

The present knowledge of yeast and fermentation has come 
by way of the following theories: (i) Physical. Naegeli sur- 
mised that the yeast cell .transferred its physical activity to the 
medium within a radius equal to three to six diameters; (2) 
Chemical. Liebig rationalized the ideas of the alchemists coming 
through Stahl a century before; he presumed yeast to be an 
unstable albuminoid which produced fermentation by chemical 
reaction; (3) Physiological. Pasteur controverted the first two 
theories by confirming the vegetable nature and action of yeast. 
His careful research gave valuable theoretical and practical re- 
sults; (4) Jtngymic. Traube, working along the same line, 
stated in 1858 that yeast secreted substances called enzymes, 
(see page 9), which- had been found independent of yeast in 
1833. In 1897 the fermenting enzyme, zymase, was separated 


from yeast and named by Buchner, who thus confirmed the 
theory/ that alcoholic fermentation is the result of the action of 
an enzyme produced by the yeast cell. 


Bread yeasts belong to the fungi, the lowest order of the 
sub-kingdom Cryptogamia or non-flowering plants, without 
leaves, stems, etc. Specifically, they are the "top yeasts" of the 
class Sac char oniyces, order cerevisiae. Top yeasts, in distinc- 
tion with bottom or lager beer yeasts, become most active at a 
higher temperature and rise to the top of the fermenting liquor, 
though they afterwards settle to the bottom of the cold wash 
water. They are identical with the distillers' yeast and the 
yeasts of the sweet English beers. Top and bottom, together 
with wine and "wild" yeasts, lactic acid and innumerable other 
bacteria, are found in the floating air dust, in the soil, on vege- 
tation, and very thickly on the skin of ripening fruits. 

Bread may be made with bottom or brewer's yeast. But its 
lower temperature of fermentation, its weaker action, its bitter 
taste and its tendency to darken the bread all tell against it; 
moreover it keeps poorly in the warm months. 1 For these 
reasons brewers' yeasts are not held to be bread yeasts in this 

Yeast breathes oxygen and feeds on albuminoids, substances 
similar to egg albumen, which have been degraded to amids and 
peptones, and on organic and inorganic salts. It also ferments 
sugars .into alcohol and carbon dioxid ; other products of fer- 
mentation, though in almost negligible quantities, are glycerin, 
succinic acid and higher alcohols.. It is believed, though not 
proven, that leavened bread owes its flavor to these latter organic 

1 "The Technology of Bread Making," Jago and Jago, London, 1911 ; 
P- 233. 


substances. As it does not secrete chlorophyll, yeast needs no 
light at any stage in its life, nor is it sensibly affected by electric 
current, by great pressure (1,800 atmospheres), or by great 
cold (130 C., or 266 F.). 

Bread yeast has these characteristics: It starts to reproduce 
below^io C. (50 F.) and is most active in reproduction and 
fermentation at 30 C. (86F., Maercher and Pedersen), when 

Fig. i. Healthy yeast cells in the process of budding. 
(Microscopic drawing by W. T. Foster.) 

it raises the temperature of the medium to 33 C. (91 F.). In 
a moist condition it will live only an hour at 44 C. (m F.); a 
moist heat of 60 C. (140 F.) will kill it in five 'minutes. Just 
as all plants contain much water, so yeast normally carries 72 
per cent. This may be reduced to 13 per cent, by slow drying 
without killing the cells, and with this amount of natural or body 
moisture they will withstand a heat of 100 C. (212 F.), or 


may be kept alive in starch, plaster of paris, etc., for years. In 
this condition yeast ceases to breathe or reproduce by sporula- 
tion (forming of spores), it remains dormant, and revives very 
slowly when it is again restored to normal conditions. 

Yeast cells reproduce by budding in a nutrient solution 
(Fig. i). Pasteur watched the yeast from the fresh juice 

Fig. 2. Saccharomyces Cerevisiae (from Jago, p. 157). a Top yeast, attest; 

b Top yeast, actively budding; c Bottom yeast, at rest; 

d Bottom yeast, actively budding. 

of grapes under the microscope: "in the course of two hours 
two cellules had furnished eight, including the two mother 
cells." 1 Yeast stops budding when it has brought the alcohol 
of the solution up to a 20 per cent, strength; and budding cells 
cease to bud when placed in a non-nutrient sugar solution, or 
when dry. In the latter case reproduction by buds gives place 
to a slow reproduction through spores unless the yeast is quite 
dry, as just mentioned. 

Yeast will reproduce in nutrient solutions which contain a 

1 "Studies on Fermentation," Louis Pasteur (Faulkner-Robb), London, 
1879 J P- MS- 


high percentage of lactic acid (the acid of sour milk) for 
instance, as much as 3 per cent. ; but it is very sensitive to 
some other organic acids like acetic (the acid of vinegar) and 
butyric, and even more sensitive to inorganic acids. Since most 
of the micro-organisms which are detrimental to fermentation 
cannot resist a high percentage of lactic acid and yeast can, 
this property is made use of in the manufacture of yeast to get 
rid of undesirable organisms (see page 26). 

Under the microscope the cell, one three-thousandth of an inch 
in diameter, is seen to be a transparent sphere or oval (Fig. 2). 
It consists of an outer membrane, a protoplasm or watery in- 
terior, and a nucleus or visible center. A young cell has thin, 
transparent walls, a transparent protoplasm, and a nucleus which 
may be invisible. Mature cells have somewhat thicker walls, and 
occasionally vacuoles or bubbles in the protoplasm; while walls, 
protoplasm and nucleus are developing granules. Old cells become 
shrunken, with thick walls, and granular structure throughout. 

The cells when not well nourished begin to break up and be- 
come auto-fermentative, die and melt down, and finally decom- 
pose with an offensive odor. 

As before stated, normal yeast contains about 72 per cent, 
water. ThejzS per cent, dry matter gives the following propor 
tions of organized substances i 1 ^ 

Cellulose^. 37 

( Albumin ^6 

Protein L . . . 

( Protein similar to gluten-casein 9 


jPegtone 2 

I'at 5 

Ash 7 

Extractive matters 4 


1 Naegeli and Loewe, from "Manual of Alcoholic Fermentation," 
C. G. Matthews, London, 1901 ; p. 41. 




C 48.5 

H 2 6.8 

N 2 11.46 

2 (+S) 30-80 



Potassium phosphate 78.5 

Magnesium phosphate 13.3 

Calcium phosphate ' 6.8 

Silica, alumina, etc 1.4 


Or, 3 

K 2 O 33.49 

MgO 6.12 

CaO 5.47 

P 2 5 50.60 

SiO 2 1.34 

SO 3 0.56 

Fe 2 O 3 0.50 




Carbon dioxide 
Succinic acid 



Fats, etc 

Pasteur 4 





Blount & Bloxam 5 

(100$ cane sugar) 







1 " Handy Book for Brewers," H. C. Wright, London, 1907 ; p. 413. 

2 Matthews and L,ott, from C. G. Matthews ; p. 125. 

3 C. G. Matthews; p. 124. 

4 Wahl and Henius ; p. 1070. 

5 "Chemistry for Engineers & Manufacturers," London, 1896; p. 201. 



The activities of yeast are three: breathing oxygen; feeding, 
and^rm^ntation^ Just how closely related these processes are 
and what their bearing is upon reproduction, are not more clearly 
understood than is the phenomena of ordinary plant life; but the 
visible life and activities of the yeast cell are now well mapped 

Breathing. That yeast needs oxygen is shown: by its ability 
to turn arterial or red blood blue; by its reduced activity in the 
fermenting liquid, after the oxygen is absorbed; by its renewed 
activity after aeration. Gay-Lussac, in 1810, first suggested that 
^oxygen starts fermentation. Later experiments showed that 
oxygen was not necessary; while Pasteur in 1861 showed that 
oxygen quickened fermentation. 

Nutrition. Yeast foods are: 1 

1. Nitrogenous compounds ! (Albuminoids as amids, etc.) 

2. Carbohydrates ( fermentable sugars, starch). 

3. Mineral matter. 

All of the substances found in the analysis of yeast (page 7) 
are furnished by the breaking up of the albuminoids, carbohy- 
drates (sugars and starch) and mineral matter (chiefly potash 
and phosphoric acid). Thus Pasteur raised yeast in a nutrient 
solution of pure water and sugar, ammonium tartrate and yeast 

Yeast as a plant is unable to feed directly on the nitrogenous 
mash substances which form its food.j^It must first digest and 
break up the albumin and albuminoids, and peptones and amids 
which are more soluble and simple so-called protein or nitrogen- 
ous forms. This degradation or digestion of the albuminoids is 

1 "Manual of Alcoholic Fermentation," C. G. Matthews, London, 1901; 
p. 41- 


attributed to what is called the proteolytic or digestive action of 
certain substances, enzymes. 

I Enzymes, once called unorganized ferments, are albuminoid 
substances which are evolved by living cells, and which are 
thought to act by catalysis. "Under favorable conditions the 
amount of material which may be changed by a given amount of 
enzyme is so great as to indicate that the enzyme ... is not 
used up by the reaction which it brings about." 1 Recent re- 
search in organic chemistry has found them in the saliva, gastric 
and other digestive juices, in animal tissues, and in vegetable tis- 
sue and cells (as in flour). They react commonly at room tem- 
peratures, are coagulated at 70 C. (158 F.), and are as a rule 

At least one proteolytic enzyme of yeast, named endotryptase 
by Hahn, 2 has been isolated. It enables yeast to digest nitro- 
genous foods. Similarly, malt is found, on extraction, to undergo 
a digestion of its albuminoids to peptones and amids. Though 
these digestive enzymes have not yet been definitely isolated, 
their action is seen to resemble that of the animal enzymes, 
pepsin and trypsin. 3 

The distiller aims to produce as little yeast as possible and is 
indifferent as to its condition. His strongly saccharine worts 
give a low yield of an exhausted yeast. On the other hand the, 
yeastmaker aims to produce a wort, rich in peptones and amids 
and comparatively low in sugars, and he gets many times the 
yeast that the distiller gets, 

We have seen that it is necessary in order to produce a healthy 
and strong growth of yeast to have a solution which is rich in 

1 "Chemistry of Food and Nutrition," H. C. Sherman, New York, 1911; 

p. 45- 

2 "Technical Mycology," Franz Lafar, London, 1910; Vol. II, Part 2, 

P- 549- 

3 Wahl and Henius ; p. 1042. 




albuminous substances, carbohydrates and mineral matter in a 
state in which they can easily be assimilated by the yeast. In 
the practice of fermentation such solutions are produced from 
various raw materials which form the mash or wort. The mash 
is the sugar solution which contains the suspended solids of the 
raw materials ; while the name wort applies to the clear solu- 
tion which does not contain any suspended solids. 

The mash constituents are malt and several grains generally 
corn and rye. 

Malt is barley or other grain that has been moistened and 
allowed to germinate, then dried. The following is the approx- 
imate composition of barley before and after 






I 3 .0 

I2. 9 




( Cane 2 8 6 o' 2 "1 

1 Maltose I ^ ^ o ! 

Sugars J. frluoose I ^ ^ ^ f 

' Levulose 07 i s I 

1 Oflrfltiif1 









main .products of the activity of yeast)! carbondioxid and 
ethylalcohol^ (grain alcohol), are the result of the fermentation 
of sugar; and it was believed until a few years ago that the 
other products of alcoholic fermentation higher alcohols, gly- 
cerin and succinic acid were also derived from the fermenta- 
tion of sugars. But Ehrlich has shown conclusively that pro- 
ducts like amyl-alcohol and succinic acid are not so derived, but 

1 C. G. Matthews ; p. 162. 

2 After malting ; Wahl and Henius ; p. 460. 


are the products of the action of yeast on albuminous deriva- 
tives, especially amino-acids. Following this discovery Ehrlich 
has isolated new products of yeast fermentation for instance, 
tyrosol, a new alcohol, derived from tyrosin. The source of 
the glycerin has not been discovered so far. 

While malting increases the sugars to about 15 per cent., the 
vital change is the production of the enzyme, diastase. Diastase 
converts the gelatinized starch of grain to fermentable sugar and 
dextrins, by hydration. The converting strength of malt is 
called its diastatic power. Diastase is partially destroyed at a 
heat of about 75 C. (167 F.). 

Starch., (C 6 H 10 O, 3 ), is the white, cellular carbohydrate that 
forms the great bulk of the mash substance. It is insoluble and 
granular. Boiling it, bursts the cells and forms a gelatinous 
paste. Diastase hydrates starch to maltose (malt sugar) and 
dextrins. When starch is converted in this manner in practice 
by the so-called mashing process, the ratio of maltose to dextrin 
produced is about 80 per cent, maltose and 20 per cent, dextrin. 
During the subsequent process of fermentation the maltose 
(C^ELjaOn) is hydrated by the yeast enzyme, maltose, produc- 
ing glucose which is readily fermentable. 

Dextrin, (C 6 H 12 O 6 ), is an amorphous, soluble gum, sometimes 
used on postage stamps. It is not fermentable, but becomes so 
if diastase is present. 

The Albuminoids are protein substances, in other words, those 
compounds containing nitrogen the enzymes, gluten, albumin, 
peptones, amids, etc. The action of the proteolytic enzymes 
breaks down the albuminoids to the simpler forms for yeast food. 

Cane Sugar or sucrose (C^H^O^), found in the malt in 
small amount, is inverted by the enzyme invertase to the fer- 
mentable sugar glucose, and the less fermentable levulose. 



PHI MrxkR v 

-Sut Arrear 



easi/y fermeata. b/e 

Slowly fermentatle 

7ior slowly 







Fig. 3. Diagram of the enzymic reactions in yeast manufacture. 

Glucose, (C 6 H 12 O 6 , called dextrose and grape sugar), is the 
readily fermentable sugar of grapes. It is less sweet and more 
soluble than cane sugar. 



in ye 


J L -oics 




a.nd boded 









-Carboy r c . ,. 
Dioxid, L EU.U- 




Fig. 4. Diagram of the mass action in yeast manufacture. 


Levulose, (C 6 H 12 O 6 , called fruit sugar), is laevorotary to glu- 
cose and is less readily fermentable. 

Cane sugar and levulose are comparatively unimportant in 
grain mashes. They become important in the manufacture of 
yeast from cane or beet molasses. But maltose and dextrin are, 
together with the hydrated albuminoids, the most conspicuous 
and also the most important products of the mashing process 
in the manufacture of yeast from cereals. While the latter 
(the albuminoids) are the principal sources of the yeast food 
the maltose and dextrin form the bases for the alcoholic fer- 

Figs. 3 and 4 show graphically the chemical changes in the 
mash, due to the enzymic actions of the malt and yeast. The 
three main reactions are: 

(1) The inversion and hydration of starch by diastase, pro- 
ducing maltose and dextrins. 

(2) The hydration of maltose, by maltase to glucose 

C 12 H 22 1 

2H a O = 2C 6 H 12 6 . 

(3) The fermentation of glucose and other sugars and dex- 
trin by zymase, to produce alcohol and carbon dioxid, 

C 6 H 12 6 = 2C.H, 5 OH + 2C0 2 . 

The proteolytic or digestive reactions are too uncertainly 
known to need a statement here. 

(Approximate. ) 

per cent. 

per cent. 

(sugars, starch), 
per cent. 



I 60 



9 en 

I ^O 


"P V<? . 


2 O 


IN-yC ' 


The process by which yeast food is released from the mash and 
assimilated by the yeast is best determined under fermentation. 

Fermentation. LafarV general definition is: "J?ermentation 
is a decomposition or transformation of substances of various 
kinds, brought about by the vital activity of fungi." At the 
present time fermentation is charged to the analytic action of 
an enzyme, called zymase, secreted by the yeast cell. 

Yeast is found to secrete at least three enzymes maltase, in- 
vertase, zymase. The first two break down the mash compounds 
into fermentable compounds ; the last, zymase, carries out actual 
fermentation. The growth of yeast in Pasteur's solution (see 
page 8) shows that its enzymes may act by synthesis as well as 
by analysis. 

The empirical formula of fermentation is 

Sugar Carbon Dioxid Alcohol 

^H^=2CO^+^2C 2 H 5 OR. 

The amount of sugar a yeast can split up in a given time is 
defined as its fermentative power', and is dependent on tempera- 
ture. The attenuating power of yeast refers to the amount of 
sugar a yeast will ultimately split up. Pasteur obtained 51.11 
per cent, alcohol from the 100 parts cane sugar which he first 
converted to 105.2 per cent, invert sugar; the remaining 48.9 
per cent, was carbon dioxid. 2 


Within fifty years it has been found that the uncertainty of 
fermentation was due to the uncertain yeasts, and that the "dis- 
eases" of beer, wine and vinegar could be avoided. The micro- 
scope revealed two important facts; that a bread yeast, for in- 
stance, besides consisting of different varieties of "wild yeasts," 

1 "Technical Mycology," L/ondon, 1899; Vol. I, p. 24. 

2 C. G. Matthews ; p. 96. 


was infested by other yeasts and bacteria which caused the 
"secondary fermentation;" also that the progeny of a single cell 
differed as much as do the different wheat plants, from seed of 
a single wheat head. Pasteur apparently rid his yeasts of bac- 
teria by sterilizing his solutions with potassium tartrate or phe- 
nol, (carbolic acid) 1 but even then the all-yeast mixture was only 
less uncertain than the infected yeasts. 2 So the better to avoid 
the bacteria and wild yeasts and to give the useful yeasts a free 
field in their solution Hansen originated his pure-culture method 
in 1879. In Hansen's method, a small portion of Koch's sterile, 
nutrient gelatin which contains yeast cells is placed on the under- 
side of a watch glass in the moist atmosphere of a bell jar. 
Those yeast specks which, under the microscope, appear as single 
cells, are first marked on the top of the watch glass. After a 
three or four-day sojourn in the moist bell jar the yeast 
colonies, which have formed from the marked specks, are sep- 
arated; Each colony furnished the seed for the pitching yeast. 

Practically all breweries and many distilleries and yeast fac- 
tories now start their mother liquor from a single cell according 
to one of the pure-culture systems. 


Dry yeast cakes made with fine grain or barley meal were 
used by the Roman bakers. 3 It has been formerly the practice 
here and abroad to mix about 20 per cent, of starch into the 
yeast cake, for the alleged purpose of drying and keeping it. 
The best modern practice regards starch as an adulterant. Pure 
yeast that is well washed and pressed dry needs no starch and 

1 "Studies on Fermentation," Pasteur (Faulkner-Robb), London, 1879; 
p. 231. 

2 Wahl and Henius ; p. 1085. 

3 " The Modern Baker, Confectioner and Caterer," John Kirkland, 
London, 1910; p. 3. 


will keep in the cake form for several weeks, if kept cool, and 
still be active and fairly sweet. Slime in yeast is due to im- 
perfect washing and to the action of destructive bacteria. 

(Comparative Tests of Pure Yeast with Yeast and Starch.) 






of C0 2 



87X 1 
8o 2 



1-14 days 

24 hours 


QI Q^ 

C 2 

V 1 yo 

77 87 

O u 

o u 

// 3 

Moufang 3 says that over-washing yeast with pure water will 
cause it to lose almost all its fermentative power after 12 to 
14 days. Washing in dilute phosphoric acid rather increases 
its power. The yeast foams and dry yeast cakes will keep for 
months. Their yeast becomes dormant and must be given time 
to revive. It is believed that the dry yeasts are largely composed 
of sporulation cells. 

Pressed yeast of good quality will keep 10 to 12 days in the 
winter and half as long a time in summer. The baker is rec- 
ommended to keep his yeast tied in a bag in a cool place and 
the bag is occasionally dipped in cold water. 4 Even in the 
summer, yeast can be economically shipped half way across the 
continent by express. The yeast, well wrapped in paper, is 
insulated in thick sawdust and boxed in wood. Such a ship- 
ment made from New York to Chicago will be in good condition 
up to a week after its receipt. 

1 T. J. Bryan, U. S. Dept. Agr., Bur. of Chem., Bulletin 116. 

2 A. Kopper, Chem. Zeit., 1909, 33 : no. 

3 Wochenschr. f . Brauerei. 

4 Kirkland ; p. 83. 


The following paragraphs on the "Transportation of Yeast" 1 
show how yeast may be prepared for a long voyage: 

"While I was employed in India I devoted much atten- 
tion to the means now in use to make yeast fit to undergo trans- 
portation for long distances and retain its fermenting energy 
in transoceanic shipments. If the yeast is to be kept for a short 
time only it may be known that the method is first to subject 
the yeast to a thorough cleaning and then to press it out as 
thoroughly and quickly as possible in a cold room. The yeast is 
then packed tight in a tin box and some fresh hops spread be- 
tween the different layers. After the box is filled, it is closed 
as tight as can be by soldering and packed in chipped ice in a 
box with double sides. Where an ice machine can be had it is 
a good plan to freeze the yeast for about seven hours at a 
temperature of 13 R. below zero, or 5 F. above zero. 

"The above manipulations are not sufficient to keep the yeast 
for many months together. I have made mixtures with dry 
yeast which made it possible to preserve it with full fermenting 
power in a dry condition for more than a year, but the mass 
with which I mixed the yeast is too much in proportion. I 
treated the ye'ast differently before drying and so I succeeded in 
obtaining a more favorable result. But the researches in this 
direction are not yet satisfactory to me, but I think I am justi- 
fied in believing that I shall succeed in so manipulating yeast in 
the dry state that it can be preserved more conveniently than 
at present and for an indefinite length of time without losing 
its fermentative power. Some years ago I sent yeast from India 
to Capetown, South Africa, and it worked well. The method 
I pursued was as follows: 

"Yeast of sound, vigorous fermenting power was mixed well 
with the double amount of filtered cold well water, to which 
1 American Brewers Review, John Hotz, 1896 ; p. 277. 


was added some salicylic acid dissolved in alcohol. After two 
hours the water was drawn off and the yeast pressed out hard 
and dried at a mild temperature, after being sprinkled once or 
twice with a weak solution of salicylic acid and alcohol. It was 
dried until the little balls of yeast could be ground into fine 
powder by stronger pressure. In order to avoid having any 
larger particles I had it sifted through a fine hair sieve and 
afterwards mixed the yeast with about three or four times the 
amount of plaster of paris. 

"This mixture should be very intimate, and the whole mix- 
ture run through the sieve repeatedly. It is then put into a 
tin box coated inside with strong paper, the box is filled as tight 
as possible and soldered up. The box was packed in a double 
chest, filling the hollow space between the walls with sawdust. 
I have also mixed yeast with plaster of paris before it was quite 
dried out, thinking the mixture would become more intimate in 
that condition, but in that case the yeast requires from four to 
seven times the volume of plaster of paris and finally does not 
keep so long. 

"Experiments with powdered charcoal were also successful, 
but I prefer the plaster. 

"When the yeast treated in the above manner arrives at its 
destination it can be used at once, that is, a quantity of the 
mixture the ratio of yeast and plaster being known is put into 
an open one-sixth barrel of sweet wort of 14 R. (64 F.) and 
the liquid well roused. This is repeated until fermentation sets 
in, which will not take very long if a sufficient amount of yeast 
is used. After the wort has begun to ferment and a fine heavy 
film appears on the surface, the whole liquid is poured into a 
half-barrel of sweet wort of 13 R. (61 F.). Here it is 
left until fermentation again sets in and the liquid thus obtained 
is sufficient to start fermentation in four barrels filled with 


sweet boiled wort of 12 R. (59 F.) and from there the fer- 
menting wort or kraeusen beer goes to the big fermenting tun, 
where fermentation is commenced at 7^ R. (48 F.)." 


Fresh pressed yeast is tasteless and has a faint and agreeable 
smell of apples, which smell becomes cheesy when stale. It is 
somewhat granular and crisp under the fingers ; a cake is elastic 
and tears with a faint "cry." Yeast not thoroughly washed, or 
containing destructive bacteria, becomes soft and slimy. A rye 
mash makes a pale yellow yeast ; a wheat mash, pale pink. The 
gray color of old yeast is due to the dead cells. 

The microscopic test is confined to the factory and the research 
laboratory. The yeast to be tested is milked with pure water in 
a burette. A drop of the fluid is put on a glass slide and gently 
spread out with a glass cover. Under an enlargement of about 
400 diameters, healthy cells appear spherical or oval, pale yel- 
low or white, translucent and not granular. 

The laboratory test of Adrian J. Brown 1 to give comparative 
activity, odor, flavor, fermentative and attenuating powers of 
yeast would not be useful to the baker or yeast manufacturer. 
Matthews also suggests that his laboratory tests would often be 
useless ; gJbpttom yeast would give a greater carbon dioxid yield, 
and yet be nearly useless as a bread leavener. 2 

August Metzler 3 of Australia used the following test : 

Weighed yeast was doughed in 100 grams flour and 80 cc. water, 
in a dish with a spoon, at 30 C. (86 F.) This dough was rolled 
on a board with 3-5 grams more flour, into a shape 4^ x 1^/4 
inches, and dropped into a paper cylinder and put in a 500 cc. 
measuring glass. The first reading is taken as zero. Consecu- 

1 " Laboratory Studies in Brewing," London, 1904 ; p. 127. 

2 " Manual of Alcoholic Fermentation," London, 1901 ; p. 274. 

3 American Brewers Review, Dec. 1902; Jan. 1903. 



tive readings are taken every 30 minutes for two hours, when 
the dough should be soft and uniform. The table below shows 
how volume readings for different amounts of yeast may be 

(100 gr. flour, 80 cc. water, 30 C. 


i gr. 


2 gr. 


4 gr. 


7 gr. 


10 gr. 



T l /. 

1 /2 




If a standard flour could be kept, this test would serve to 
check the yeast for time and quantity. Where the yeast was a 
standard compressed, the behavior of different flours under 
fermentation could be roughly estimated. 


In the previous paragraphs we have seen that to produce yeast 
it is necessary to prepare a sugar solution rich in albuminous 
matters which can be easily assimilated by the yeast, and which 
also contains enough mineral matter for its use. The process 
of manufacture consists of: (i) The production of a suitable 
solution for the growth of the yeast; (2) The addition of seed 
yeast to this solution; (3) Multiplying the seed yeast in this 
sugar solution; (4) Separating the yeast crop from the solution 
and putting the yeast in marketable shape by washing and 
pressing it. 

There are two processes of yeast manufacture, which differ 


radically in the method of separating the yeast crop from the 
sugar solution. The older method is called the Continental or 
Vienna process. The mash is generally made up of a mixture of 
equal parts of malt, rye and maize; and the mashing is so con- 
ducted that a foam forms during the fermentation. This foam 
contains most of the yeast, which is separated from the mash 
by skimming off the foam. The more recent process is called the 
aeration or wort process. In this method the manufacturer does 
not depend on a foam, but allows his yeast to settle out of solu- 
tion or separates it by means of a centrifugal machine similar 
to a cream separator. 

It is obvious that in the aeration process a clear wort carrying 
no suspended solids must be used for the growth of the yeast; 
otherwise these solids would settle with or be separated with the 
yeast and would make the recovery of a pure product impossible. 
In the old Vienna process, as before stated, only cereals can be 
used ; and rye is one of the most important ingredients of the 
mash, because it is necessary to the production of the foam with- 
out which no yeast can be produced. But in the aeration pro- 
cess where foam is undesirable other materials can be used 
potatoes, molasses, beets or cane-sugar. 

Yeast made by the old Vienna process is considered to be of 
better quality than that produced by the aeration process. How- 
ever, very good yeast can be made by the aeration process and 
the latter, gives a greater yield of yeast and a small yield of 

The following approximate figures show the difference : 

Grain Yeast Proof spirits 

100 pounds 12-15 pounds 6^-7 gallons 

100 pounds 18-22 pounds 5 gallons 


2 4 



In the last few years the aeration process has been considerably 
improved and the yield of yeast raised as high as 30 and even 
35 pounds from 100 pounds of grain, and the alcohol has pro- 
portionately decreased. 

With the- principal differences between the two processes in 
mind, the common practice in both methods will now be given 
in more detail. (See diagram, Figs. 5 and 6.) 


1. Preparation of the Chief Mash. 

(1) Cleaning and grinding the grain. 

(2) Mashing or saccharifying. 

(3) Cooling. 

2. Preparation of the Seed Mash or Seed Yeast. 

1 i ) Mashing of seed-yeast. 

(2) Souring of seed-yeast. 

(3) Cooling and setting with stock or mother yeast. 

3. Treatment of Chief Mash. 

1 i ) Adding the ripe yeast-mash. 

(2) Fermentation. 

(3) Skimming off the yeast foam. 

(4) Distillation of the ripe chief mash to recover alcohol 

(residue, slop). 

4. Treatment of Foam. 

(1) Foam cooled by diluting with cold water. 

(2) Sifting through fine silk to eliminate particles of solids 

skimmed with yeast. 

(3) Washing the yeast with water (two or three times). 

(4) Settling from water. 

(5) Pressing in filter presses or in bags. 

(6) Forming into packages, cakes, etc. 


Material. 800 pounds kiln-dried malt, 800 pounds rye, 800 
pounds corn. The corn is ground to a meal and run into a cooler 
or mash tub (Fig. 7) where it is boiled with direct steam under 
continuous agitation. It is not customary to cook the corn under 
pressure a practice usually observed by distilleries. In a sep- 
arate mash tub, rye meal and malt meal are mashed with water, 
and the cooked corn is added to this mixture. The temperature 
of the three cereals are so regulated that their combined tempera- 
ture in the mash tub (Fig. 7) is about 63-65 C. (145-148 F.) 

The mash is now allowed to stand for about an hour to allow 
the malt diastase to convert the gelatinous starch to maltose, and 
is then cooled through the cooling coils in the tub to a tempera- 
ture of about 20 C. (70 F.). At the same time the mother 
yeast or seed mash, which has been previously prepared, is add- 
ed to the mash in the fermenter (Fig. 8) and the fermentation 
is thus started. It is customary and advantageous to add some 
slop (spent mash from a previous distillation) to the mash in the 
fermenter. This slop contains valuable nourishment for the yeast 
and also a certain amount of lactic acid which will retard the 
reproduction of obnoxious bacteria and will stimulate the yeast. 

The yeast mash, already spoken of, is made from 150 pounds 
rye and 150 pounds malt, both ground and mashed in the smaller 
so-called yeast tubs, in the same manner as the chief mash. Af- 
ter mashing the yeast mash, it is allowed to undergo a lactic acid 
fermentation which is induced by the lactic acid bacteria intro- 
duced with the malt or rye; or better, by adding a lit'tle soured 
yeast mash taken from a previous yeasting ; or by the introduction 
of pure-culture lactic acid bacteria. The yeast mash sours for 
12 to 24 hours, when it will contain from y 2 to 2 per cent, of 
lactic acid. The function of this lactic acid has been already ex- 
plained (see page 6). 


Oi/t/e t 


Fig. 7. Diagram of mash tub. 




Fig. 8. Diagram of fermente: . 

After souring, the yeast mash is cooled to fermentation tem- 
perature and fermentation is started with stock yeast, or with 
mother yeast from a former fermentation, or with pure-culture 


yeast. The fermentation is continued for 10 to 20 hours, or un- 
til the yeast cells are fully developed: this depends on the tem- 
perature and the amount of stock yeast used. The ripe seed 
yeast or yeast mash is finally added to the chief mash as already 

Fermentation begins in the chief mash, bubbles of carbon di- 
oxid come to the surface and the temperature rises. The increase 
of temperature quickens the fermentation and the bubbles of car- 
bon dioxid become entangled in the slimy albuminoids of the 
rye and form a foam several inches thick on top of the mash. 
At first the foam is transparent, but as the rising gas begins to 
bring up the newly generated yeast cells from the mash, the foam 
grows first milky and then to a thick cream. By the appearance 
of the foam the practical yeast-maker judges when the yeast is 
ripe for skimming. Ripe cells are rounded and vigorous, and 
rich in glycogen. 

Skimming is done with dippers; or long paddles are used to 
push the foam to an opening in the top of the fermenter. The 
skimming is continued as long as foam forms on the surface of 
the mash, and the foam is at once run into cold water to check 
further activity of the yeast which may lead to auto-fermenta- 
tion. For in the absence of fermenting material the enzymes of 
active yeast attack the yeast protoplasm at fermentation tem- 
peratures. As the yeast foam, mixed with cold water, is run over 
fine screens of metal or silk to separate it from particles of the 
mash which ' have also been skimmed off, the yeast and water 
pass through the fine meshes. The yeast settles to the bottom of 
the settling tank (Fig. 9), the water is syphoned off and fresh 
cold wash water added. This process of washing can be repeated 
several times. After the last washing, the water is completely 
drained off and the yeast, which looks like thick cream, is ready 


< x -\ Yeast 


Fig. 9. Diagram of washing tank. 


for pressing. In former times the yeast cream was run into linen 
bags and the water pressed out in a screw press. Modern fac- 
tories all use filter presses (Fig. 10) into which the yeast cream 
is pumped under a pressure as high as 200 pounds to the inch. 
The yeast remains in the press cloth between the plates and the 
water runs off by way of the spigots. After the press is full it 
is opened and the pressed yeast is turned into a trough or bin, 
from which workmen shovel it into various machines which mold 
it into cakes or packages for the market. 

Yeast is enclosed in paper or tin-foil wrappers for small con- 
sumers, or put up in paper-lined wooden boxes for bakers or 
for express shipment. It must be kept cold during storage and 
transportation. If good yeast is properly stored it will keep for 
several weeks ; if it is of poor quality or allowed to get warm it 
will deteriorate very quickly. 

We have followed the process of fermentation up to the time 
when the yeast foam was skimmed off and will now speak briefly 
of the remaining mash. Not all the yeast can be recovered by 
skimming; a certain percentage remains in the mash and com- 
pletes the fermentation of the sugar contained therein. When 
the fermentation ends, the mash holds about 5-7 per cent, of 
alcohol, which is recovered by distillation. The residue from 
distillation is called slop or wash, used for cattle feed. But some 
of the slop is clarified by settling and returned to the fermenter 
as already mentioned (see page 26). 

It will be seen that the Vienna or Continental process hinges 
entirely upon the formation of a foam during fermentation. The 
composition of the raw material, the treatment of the same in 
cooking and mashing, the temperature of fermentation, the 
method of yeasting all are planned with the object of bringing 
about the proper kind of foaming. 



Disturbances in fermentation may occur at any of the steps in 
the process. Infected vessels or improper treatment of the foam 
are most likely to produce bad results, which manifest themselves 
in a low yield of yeast and alcohol and in a poor quality of yeast. 
Then there will be difficulties in settling and pressing and the 
yeast will have a low fermenting power and will not keep any 
length of time. Sometimes the poor quality of the yeast can be 
laid to the excessive use of starch, which at the best is an adul- 
terant (see page 16). And the starch may not only unneces- 
sarily dilute the yeast but it may in itself hold bacteria which 
will decompose the yeast. 


The aeration process (see diagram, Fig. 6) does not depend 
on the foaming of the mash; a clear wort is used in this pro- 
cess from which the yeast settles out or is separated by means of 
a yeast separator made by the DeLaval Separator Co. The wort 
is commonly prepared from ground grain, or sometimes from 
molasses. A brief outline of the aeration process : 

1. Preparation of Wort. 

(1) Grinding. 

(2) Mashing. 

(3) Souring of mash. 

(4) Filtering for the wort. 

(5) Cooling of wort. 

2. Fermentation. 

(1) Setting with seed yeast. 

(2) Fermentation under continuous aeration. 

(3) Separation of yeast by settling or "centriffing." 

3. Pressing and Packing the Yeast. 


y Material. 700 pounds green malt, 150 pounds rye, 700 pounds 
corn, 150 pounds malt sprouts. The rye and malt are ground, 
not too fine so as to preserve the hulls for filtering material 
and then mashed as in the Vienna process. The corn is first 
cooked with water before adding to the rye and malt mash. 
The final temperature of mashing is now about 63 C. (145 F.). 
The mash is allowed to stand about 15 hours for souring, care 
being taken to keep the temperature at about 50 C. (120 F.). 
At or above this temperature, a very pure lactic acid is formed. 

In order to insure a pure lactic acid bacteria, a small portion 
of previously soured mash is prepared with pure culture lactic 
acid bacteria. The acidifying of the mash, and especially the 
quality and percentage of lactic acid produced in the mash, is 
one of the most important operations in the production of a 
good quality and large yield of yeast by this process. Failures 
were frequent in the early days of the aeration process, until 
the yeastmakers learned how to produce the proper conditions 
and proper acidity for fermentation. 

After souring, the mash is heated to about 66 C. (150 F.) 
and stands until the lactic bacteria are dead. Then the mash is 
pumped into a tub with a perforated false bottom, like those used 
in making beer. Here the mash stands long enough to let the 
solids settle on the perforated bottom; then the mash is drawn 
off as it filters through the layer of solids. This wort is pumped 
back and refiltered until it is perfectly clear, then run into a 
fermenting tub. Compressed yeast for seed is diluted with a 
little wort or water and mixed with the wort running into the 
fermenting tub. Pipes lead into the bottom of the tub and a 
strong current of filtered and purified air is blown through these 
pipes and up through the wort. After the wort has been run 
off so that the surface of the grain appears,- the latter is sprayed 


with hot water to extract the remaining wort. This extract is 
also run into the fermenting tub, until presently the extract 
that filters through the grains is almost pure water. 

Now the flow of water is stopped and the grain discharged 
from the filtering tub. This spent grain serves for cattle food. 
In this process the fermenting tub is filled only half full, be- 
cause the excessive agitation caused by aeration creates a high 
foam which would overflow the tubs if they were too full. Ex- 
cessive foaming is sometimes checked by covering the surface of 
the wort with a thin layer of pure neutral oil or fat. The tem- 
perature of fermentation is ke^t at an even 29 C. (84 F.) by 
the cooling coil in the fermenter. 

Fermentation goes on rapidly and is over in about 10 hours, 
for the wort holds only about 4 or 5 per cent, of extract. 

The fermented wort is drawn from the fermenting tub and 
cooled at once to preserve the vitality of the yeast. Then it is 
either run into settling chambers to separate the yeast or, in the 
best modern practice, is turned directly into the centrifugal sep- 
arators. Yeast is separated out in a thick cream, cooled on 
small surface coolers and pumped into the filter press to further 
dry it. 

The aeration process has been modified and now yields a very 
high amount of yeast chiefly because of the lower fermenting 
temperature, very thin wort, a large amount of seed yeast, and 
very heavy aeration. 

Disturbances in the fermentation are due to the same causes 
as in the old Vienna process. Strong aeration greatly increases 
the danger of infecting the yeast with mycoderma and other 
fungi which resemble yeast in appearance but have no ferment- 
ing power. Aeration greatly stimulates their growth and aera- 
tion-process yeast has often been found to contain as high as 50 
per cent, of mycoderma. However its action in dough is nil. 



There are two general methods of bread making, called the 
straight dough and the sponge methods. In the straight dough 
method all the ingredients, flour, water, salt, shortening and 
yeast, are mixed together; and after a sufficient length of time 
the yeast will have caused certain chemical and physical changes 
in the composition of the dough and the dough will be ready for 
baking. In the sponge method yeast or barm has been made up 
with a given amount of slack dough called the sponge which will 
form say one-half of the batch for baking. After fermentation 
has proceeded until the slack sponge has risen twice and is 
swarming with fresh young cells, this sponge is made up with an 
equal amount of new dough and again set aside to ferment. This 
second batch represents the entire amount to be baked; it is 
tighter, and the fermentation begins again from the vigorous 
yeast cells. 

In the first process, the "straight dough," about 1-1^/2 per cent, 
by weight of compressed yeast is used. While this is enough, it, 
is not the limit to the amount of sound, fresh yeast that can be 
used. Very little reproduction or budding will go on. Much 
yeast will simply cause the fermentation to be complete in a 
shorter time. As a matter of fact bakers more often use too 
little yeast. The fermentation goes on slower and other ferments 
have more chance to begin their action and perhaps introduce 
bad flavors. 

On the other hand, the sponge dough, because it is much 
smaller than the final batch and because it is made so as to 
assist budding and reproduction of the yeast, is started with a 
much less amount of yeast. Some Scotch bakers make their first 
sponge only one-fourth the final batch, use this first sponge as a 


starter for a second sponge and then make their final dough 
from this second sponge. Of course they must be careful to 
"take" the sponge each time before fermentation has gone too 
far. Otherwise other undesired fermentations will have set in 
arid their bread will be dead and have a poor flavor. Jago 1 
gives a very graphic description of the results of "taking" the 
dough at various stages in its fermentation. 

"A very useful lesson may be learned by making a batch say of 
20 pounds of flour, into a slack dough, with a full allowance of 
distiller's yeast, say 3 ounces ; salt and water in proportion, and 
working the batch fairly warm. Let a piece be cut off and 
molded into a loaf immediately the dough is made, and at once 
baked the result will be a close, small, very moist loaf, not 
much bigger than the piece of dough cut off. Next bake a 
similar loaf from the same piece of dough at the end of every 
hour from the time of starting, keeping the main mass covered, 
and in a warm place. An instructive series of changes will be 
observed in the successive loaves. In boldness the bread im- 
proves for some hours, then remains stationary, and finally 
becomes "runny" and flat. The color of the crust is at first 
"foxy," then of a golden yellow or brown tint, and finally ab- 
normally pale. The crumb during the first three or four loaves 
of the series gradually improves, and becomes more bloomy, 
then changes to a greyish white, losing the bloom, and then 
"saddens" and darkens, becoming a dull, cold grey, merging 
ultimately into a brown. At the same time it becomes .ragged 
on the outside edges, and dark when a soft crust has been pro- 
duced by two loaves being in contact with each other in the oven. 
In flavor, the first loaf will be sweet, but "raw" and "wheaty," 
characters which will be lost as fermentation proceeds; at its 
1 "Technology of Bread-Making," London, 1911 ; p. 433. 



best the raw taste will be gone, leaving only a sweet clean-palate 
flavor. This will be succeeded by a gradual disappearance of 
the sweetness, the bread being neutral and tasteless; at the 
same time the loaf will have lost its moisture, and will be harsh 
and crumbly. As fermentation is pushed still further, the bread 
commences to be "yeasty" (to taste of the yeast) ; but this de- 
pends somewhat on the original soundness or otherwise of the 
yeast. This condition merges into one of slight sourness, first 
of pure lactic acid flavor, accompanied by buttermilk odor; but 
gradually becoming worse, until, finally, not only is the taste of- 
fensive, but so also is the smell, partaking not only of sourness 
in character, but also of incipient putrefaction and decomposi- 
tion. During these latter stages the bread again becomes soft 
and clammy." 


Flour dry matter 1 

Fermented dough dry matte *f 

sugars as 

sugars as 

sugars as 

sugars as 

1.6 7 




AX7faV flour 








12 O 

1 1 A. 

I O 

7*\ I 

O ^ 


J r ) 

O 2 

I "* 

10' i 
C7 T 

I I 



When yeast is worked up in the dough it finds the same sub- 
stances that were in the manufacturer's yeast mash, but in dif- 
ferent proportions and in a semi-solid condition. For instance, 

1 Jago ; p. 334. 

2 U. S. Dept. Agr., Off. Exp. Sta., Bulletin 28, 1898 ; p. 28. 


the mash was highly saccharine and in*a form readily ferment- 
able; but flour contains much less sugar, and the soluble protein 
is somewhat lower because wheat has more non-soluble protein, 
as gluten. 

Yeast is put in dough for two reasons, the main one being to 
produce leavening gas; and the other reason is to improve the 
flavor and to increase the solubility of the gluten both by chem- 
ical action. The reactions brought about by the yeast and, later, 
by the heat of the oven, are 1 : 

1. Fermentation of carbohydrates and production of carbon 
dioxide and alcohol. 

2. Production of soluble carbohydrates, as dextrin, from in- 
soluble carbohydrates; as starch. 

3. Production of lactic and other acids. 

4. Formation of other volatile carbon compounds. 

5. Change in the solubility of the protein. 

6. Formation of amid and ammonium compounds from solu- 
ble protein. 

7. Partial oxidation of the fat. 

i. The first is the most prominent reaction the fermentation 
of the sugars by the yeast, which first hydrates them to glu- 
cose and then splits these up into alcohol and carbon dioxid. 

Glucose Alcohol Carbon dioxid 

C 6 H 12 6 = 2 G 2 H 5 OH..+ 2C0 2 . 

Practically all flours contain more than enough sugars to carry 
on a satisfactory leavening reaction with yeast. It was early 
recognized that leavening bread gave off carbon dioxid; 2 and 
later Girard set at rest the doubt as to the reaction being an al- 
coholic fermentation, when he found 0.25 per cent, of alcohol in 

1 U. S. Dept. Agr., Off. Exp. Sta., Bulletin 67, 1899. 

2 For method of determining CO 2 in dough, see Exp. Sta. Bulletin 67, 
1899; P- 12. ^i 


a raised dough. Pohl 1 also found alcohol (0.075 P er cent.) in 
dough, and Birnbaum 2 found it in baked bread (0.314 per cent.). 
Acidity from lactic and acetic acids may be due, not entirely to 
bacteria, but to alcoholic fermentation, in case these acids are 
intermediate products. 3 

Starch itself seems to be eventually drawn into the first re- 
action ; first by the inverting power of the original flour enzymes, 
and secondly by protein matter altered by the yeast. This will 
account for the paradox that after fermenting the dough it often 
carries more sugars than before fermentation. 

In ordinary bread making the lost substance is largely divided 
between about I per cent, of carbon dioxid and a little over 
i per cent, of alcohol. 4 

2. The production of soluble carbohydrates from the starch is 
caused by the oven heat alone and the starch must be gelatinized 
before this can occur. Gelatinization begins at about 65 C. 
(149 F.) and the yeast has already died at 60 C. (140 F). 

3. The sourness of bread has received much attention, because 
it seems not to depend entirely on the actual mensurable acidity. 
Yeast itself does not cause acidity but since compressed yeast 
often contains lactic acid bacteria, and acetic and even butyric 
ferments find their way in either through the yeast or the flour 
or through unclean utensils, secondary fermentations begin just 
as soon as the yeast fermentation subsides. Jago concludes that 
"bakers' sourness is accompanied by other changes in the con- 
stituents of the bread in addition to the development of acidity ;" 5 
and he adds that lactic acid makes up about 95 per cent, of the 

1 Z. angew. Chem., 1906, 19, 668. 

2 Buchner. 

3 " Das Brotbachen," Braunschweig, 1878; p. 252. 

4 Exp. Sta. Bulletin 67, 1899 ; p. 33. 

5 p. 446. 


acid and the rest is acetic and perhaps a trace of butyric acid (in 
case of putrefaction). 1 As is the case in the yeastmaker's mash, 
none of these objectionable fermentations need be expected where 
healthy clean yeast is used and the dough is taken in time before 
secondary fermentation sets in. 

Besides the acid after-fermentation bacteria, one authority 2 
charges yeast with having carried "rope" infection into the bread. 
This so-called potato bacillus is, however, generally believed to 
come through the flour or from unclean utensils. 

4. Some of the distinctive flavor of leavened bread seems to 
come from the compounds, succinic acid, tyrosin, higher alcohols, 
etc., which are formed when the yeast feeds on the soluble pro- 
tein (see page 8). Yet it is a curious fact that in a series of 
comparative tests in which 18 known and 15 unknown varieties 
of yeast were used, the resulting breads were alike in flavor and 
odor. 3 

5. As fermentation progresses the dough "slackens" because 
its gluten is being slowly dissolved by the small percentage of 
acids forming. Likely enough the yeast itself has some action on 
gluten as well as its well-recognized digestive action on the 
albuminoids; though it is known that dough without any yeast 
will slowly slacken because the flour enzymes are busy degrad- 
ing both starch and protein. 

6. A small portion of the flour protein is in amid forms which 
is lost when the yeast converts the amids to ammonia. 

7. The breaking up or oxidation of the fat does not depend 
at all on the yeast, but on the heat of baking. 

1 p- 448. 

These volatile bodies caught in sulfuric acid gave carbon sufficient for per cent, carbon dioxid, (Exp. Sta. Bulletin 67, 1899 ; p. 16. 

2 Wisconsin Station Report 1898; p. no. 

3 Ruth G. Wardall, in Journal of Home Economics, 1910 ; 75. 



"Summing up the changes in panification they are alcoholic 
fermentation of the sugar, softening and proteolytic action on 
the proteins, and a limited diastasis of the starch." 1 The total 
loss of bread substance has been variously guessed at or esti- 
mated, by Dauglish at 3-6 per cent., Vorhees 3-4, Fehling 4.21, 
Jago 2.5, Heeren 1.57, Graeger 2.I4. 2 

In the dough, then, the yeast is given an opportunity to start 
fermentation, but the tight nature of its new home will not allow 
it to travel for its food. Hence it must soon begin to want for 
food and air and soon begin to choke in its own excrement. The 
tighter the dough the less chance there is for it to bud and re- 
produce to any extent. 

All this explains why a sponge-process batch is started with 
a slack dough. Here the yeast has much more freedom in its 
semi-liquid surroundings and can reproduce ; when the dough is 
made from the sponge the latter contains more than enough 
vigorous yeast cells to be distributed throughout the tighter 
dough. Each time the dough is pulled over, the yeast within is 
given a new lease of life. However, at best, yeast does not 
greatly multiply in either sponge or straight dough. 

Lindet's observations showed him that there were more cells 
in slack dough, but less enzymic action ; the reverse held for 
dense doughs. An increase from 20 to 30 fc. (68-86F.) 
favored multiplication and decreased enzymic action. Aeration 
favored multiplication but was not indispensable. He observed 
that at 20 C. and for 18 hours time, yeast in dough in the 
amounts 1/1,000, 2/1,000, 4/1,000 and 8/1,000, increased in the 
amounts 8.4, 6.4, 3.7 and 1.8. While if too much yeast was 
used it decreased in amount. 3 

1 Jago ; p. 424. 

2 Exp. Sta. Bulletin 67, 1899; p. ji. 

3 Compt. rend., 150, 1910; 802. 


Yeast dies in the dough when the heat goes above 60 C. 
(140 F.). And the reactions from then on are due to the heat. 
Thus a baked loaf contains much gelatinized starch in the crumb, 
and the crust is composed partly of caramel from the sugar and 
of dextrin from the starch. 


Barley bread four thousand years old, taken from the tombs 
of Egypt, showed yeast cells under the microscope. This an- 
cient yeast came from the "leaven," which was merely a portion 
of dough taken from a previous batch, and well crowded with 
all manner of yeasts, wild yeasts and bacteria. As a result 
leavened bread contained its full share of lactic and other flavors 
which these mixed ferments set up. This kind of ferment starter 
has been standard for centuries. The Scotch barm and the po- 
tato ferment are modifications of the leaven, in which the mixed 
yeasts from an original spontaneous fermentation are so treated 
that bread yeasts become predominant : lactic acid bacillus, which 
seems to have its function in giving a buttermilk flavor, is en- 
couraged in the barms. After the bakers began to go to the 
brewer for his top or bottom yeasts, they found that they could 
save themselves time and money ; and later the industry of com- 
pressed yeast making has driven barms and potato mixtures out 
of progressive regions. Compressed yeasts have also helped to 
make straight dough and short fermentation recipes more 

In some districts bakers and especially housewives still make 
their own ferment. Potatoes are boiled to gelatinize the starch 
and dissolve the protein; the boiled potatoes, or preferably the 
water from their boiling is allowed to ferment spontaneously 
or is started with a cake of compressed yeast. Hop water, added 
to the spontaneous or "virgin" ferment, helps markedly to check 


troublesome varieties of yeast and bacteria ; and raw flour gives 
added nourishment to the yeast which feeds on its protein. The 
yeast also appears to convert some of the flour protein into 
enzymic compounds which hydrolize the potato starch 1 to sugars 
for the yeast. The mixture of potato water, flour and yeast is 
used entire by the baker, and one of its virtues is that it is so 
rich in yeast food that yeast goes on growing in the dough. 

Jago 2 quotes the following process for the manufacture of 
a malt-and-hops yeast: "Forty gallons of water and 2. pounds 
of sound hops are boiled together for half an hour in a copper, 
and then passed over a refrigerator, and thus cooled to a tem- 
perature of 71 C. (160 F.). The liquor passes from the re- 
frigerator to a stout tub; \y 2 bushels (about 63 pounds) of 
crushed malt are then added, and the mixture thoroughly stirred. 
The mash is allowed to stand at that temperature for iy 2 hours, 
filtered from the grains, and then rapidly cooled to 21 C. 
(70 F.). The passage over the refrigerator serves also to 
thoroughly aerate the wort. Spontaneous fermentation is then 
allowed to set in, and the yeast is usually ready for use in 24 
hours, but is in better condition at the end of two days. All fer- 
menting tubs, and other vessels and implements used, are kept 
clean by being from time to time thoroughly scalded out with 
live steam. The result is the production of a yeast of very high 
quality." Jago and Kirkland both give detailed descriptions 
of the making of "virgin barm" (a malt-and-hops spontaneous 
ferment) and "Parisian barm." 

Boutroux 3 states that in France a portion of the dough is 
taken for the leaven of a future baking; it is mixed with equal 
amounts of flour and water and put away for four or five hours. 

1 Jago ; p. 422. 
* Ibid. ; p. 246. 
3 " Le pain et le panification," Paris, 1897 ; p. 23. 


It is again mixed as before and again let stand. Several repe- 
titions of this greatly multiplies the legitimate yeast at the ex- 
pense of the harmful vegetation. This leaven forms about one- 
third of the dough for a baking somewhat more in winter and 
less in summer. 

Compressed yeast is made or expressed to practically all parts 
of the country. But there always will be regions where yeast can 
only be obtained at intervals measured by days or weeks. In 
these cases the baker must either rely on baking powder, or he 
must make stock yeast that can be drawn on. The following 
quotation from Baker's Helper will cover this contingency : 

''When one gets in the western country he finds quite a few 
jobs where he is compelled to make his own yeast. This recipe 
works in both high and low altitudes. Here the altitude is seven 
thousand four hundred and forty feet above the level of the 
.sea. This is the method I suggest : 

"Take seven pounds of potatoes, wash them clean then peel; 
put the potatoes and peelings on the stove and boil in a pot large 
enough to keep them covered with water. Boil till the potatoes 
.are soft and tender (the tenderer they are, the easier they are 
to mash). When they are boiled enough, take them off the stove, 
take out the potatoes and throw the peelings away, but save the 
water they were boiled in ; add enough more water to make seven 
quarts ; put the water back on the stove to boil. 

" While the water is boiling, put the potatoes into a bowl and 
mash; then add three pounds of bread flour to the potatoes, 
stirring with the masher until they cool off so that you can put 
your hands in; rub this between the hands like pie dough, so 
that you get the potatoes and flour mixed well. When the seven 
quarts of water boil, take off the stove and add slowly to the 
flour and potatoes, stirring continually with an egg whip. After 


the seven quarts of water are in, strain the mixture through a 
sieve or colander; let this mixture set two hours. By that time 
it will be cooled down to about 90 degrees ; then add six cakes of 
'Yeast Foam' dissolved in two quarts of water at about 80 
degrees. Stir well, then let it set for four hours more, during 
which time it will form a foam on top and sizzle. 

"At the end of four hours add enough water at 75 degrees to 
make sixteen quarts in all ; add about eighteen pounds of bread 
flour and mix good and smooth. Let this set four hours ; in that 
time it will rise and break. Add sixteen quarts water at 60 de- 
grees, six cakes 'Yeast Foam' dissolved in some of the water, 
two and three-quarter pounds of sugar, two and three-quarter 
pounds of lard, one and one-half pounds of salt, and add enough 
flour to make a good working dough. Let this rest eleven hours 
and scale out; mold up and pan. Let it prove and bake. This 
will make 60 three-pound loaves of good fine-eating bread. Here 
I start my yeast at 8 o'clock in the morning; let it set until 10 
o'clock; then mix in the 'Yeast Foam'; then at 2 o'clock I 
mix in the rest of the water to make the sixteen quarts and the 
eighteen pounds of flour; at 6 o'clock I mix in the sugar, lard, 
etc. ; set till 5 A. M., and scale out and pan. I hope that this 
will help some brother baker, as I know it is reliable." 


As late as 1898 the Federal Department of Agriculture held 
the theory that "the fermentation of the dough may also be se- 
cured by the enzymes naturally present in the flour. This 
process of bread-making is known as the salt-rising method. 
A convenient quantity of wheat meal and corn meal is mixed 
with a little salt and hot milk and set in a warm place. In the 
course of a few hours fermentation ensues and the whole mass 
becomes porous. In this condition it is mixed with the wheaten 
flour to form a dough, which, when set aside in a warm place, 
undergoes a fermentation which in many respects is similar to 
that produced by yeast." 1 

This enzymic theory of salt-rising fermentation was not 
allowed to stand ; for bread made by this process was very uncer- 
tain and the fermentation gave symptoms that enzymic action did 
not explain. 

Kohman found that this bread rises best between 40 and 50 
C. (i04-i22 F.), that it could be made without milk, but that 
both milk and malt extract were beneficial. Milk seems to 
quicken the leavening and to increase the amount of gas given 
off. This bread needs only one rising, and it is wise to mold up 
the newly-made dough from the risen sponge and put in pans 
at once. This is probably because the proteolytic (digestive) ac- 
tion of the salt-rising ferment is much more rapid on the gluten 
than is yeast. The function of the salt seems to be to prevent 
objectionable fermentation from starting up at the same time, 
such for instance as lactic and butyric which spoil the flavor of 
the bread. 

Bureau of Chemistry, Bulletin 13, "Foods and Food Adulterants,'* 
1898; p. 1301. 


Salt-rising bread is slightly sour, like Vienna bread ; it is also 
very white, fine and evenly grained and has a distinctive flavor 
and odor not found in yeast bread. But the process is uncertain. 
One day the dough may rise readily and the next day it may have 
to be remolded with compressed yeast. Since no yeast nor sour 
dough is used it is evident that the source of the so-called spon- 
taneous fermentation must be either air, or the flour or milk. 
It has been the common impression that the salt-rising reaction 
is most dependable when the dough is mixed in a certain room 
for a period of time. Mrs. Rohrer has suggested that the re- 
action seems to fail in a well-sterilized room. 

And because this process is both good and uncertain it has 
been thought worth while to try to isolate the fermenting prin- 
ciple ; and to endeavor to put this agent in the hands of bakers 
in as dependable a form as is compressed yeast. Several in- 
vestigators have presumed that either yeast spores or bacteria 
from the air found their way into the dough and set up fermenta- 
tion just the same as the leaven or "Sauerteig" ferment. Both 
yeast and bacteria are found in leaven and "Sauertig;" but sev- 
eral scientists, among them Henry A. Kohman, 1 have made salt- 
rising dough that contained no yeast cells but literally swarmed 
with bacteria. 

These bacteria must enter the dough, either with the milk, the 
flour, the cornmeal, or from the air of a well-inoculated room. 
But a series of selective experiments in which first cornmeal, 
then milk were omitted, while the mixing was done in a sterile 
atmosphere, suggested that the cornmeal was the source of the 
bacteria. In fact both flour and cornmeal may carry these fer- 
ments, though flour seems less liable to; for good results are 
gotten with pure flour and cornmeal not too thoroughly cleaned 

1 See the series of papers by this author in Bakers Review, beginning 
August, 1911. 


in the milling. But the fact is that air, flour, meal and milk may 
all supply these ferments. 

The next question to solve was, Is the salt-rising bacteria a 
single variety? To answer this, Kohman made a set of plates 
from a salt-rising "emptyings," which contained bacteria but no 
yeast. A number of tubes were inoculated, incubated and a se- 
lection made from a tube which showed fermentation. It is not 
practicable to use sterile flour in baking tests, so Kohman con- 
tented himself with enlarging his pure culture colony to the 
point where it could be used in a dough. Sterile milk was in- 
oculated with his pure culture, incubated 17 hours and the sponge 
then made with this milk. The sponge dropped in two hours, 
when it was made into a dough, molded at once and put in pans. 
It rose well and when baked had all the characteristics of salt- 
rising bread. 

These experiments have settled definitely that the salt-rising 
organism is a separate variety which it is possible to use from 
pure culture, and a salt-rising yeast, made from dry batter, was 
used with uniform success for a month in one bakery. Salt- 
rising ferment is now manufactured and sold in this country by 
two separate companies. The ferment produced works uni- 
formly and well. 

Kohman carried his research farther. He found that there 
was no alcohol produced by this process and that the leavening 
gas was made up of about two parts hydrogen and one of car- 
bon dioxid and no hydrocarbons; so he suspected that the fer- 
mentation loss was less than in yeast bread. And his compara- 
tive tests confirmed this. 

Bread fermented normally from Kansas patent lost 5.15 per 
cent, in weight, bread put into pans at once on mixing lost 1.81 
per cent., and salt-rising bread lost only 0.44 per cent. 


Kohman concludes that the ordinary salt-rising fermentation 
is brought about by bacteria which act principally on the sugars 
of the flour and milk and especially on milk casein. These 
bacteria seem to consist of a mixed flora, some of which as spores 
live through the boiling temperature and would be found in 
batter from boiling milk. While others, not capable of forming 
spores, died at a temperature of 77 C. (170 F.). Among these 
was the variety separated for his pure culture; this was thought 
to belong to the coli group the same that was called bacillus 
levans by Wolffin and Lehman. None of these varieties kept in 
liquid media over 24 hours, but could be made up in a dry starchy 
cake for indefinite future use. 

A standard recipe is : Cornmeal, salt and soda are thoroughly 
mixed and stirred into enough hot milk or water after boiling, 
to make a batter of the consistency of corn meal mush. This 
batter or "emptyings" as it is commonly called is kept in a warm 
place 15 to 20 hours or until it becomes light and shows the evolu- 
tion of gas, and is then mixed with flour and water to make a 
slack sponge. The sponge is allowed to come up well, which may 
take from one to three hours, and is then mixed with the re- 
mainder of the ingredients to make a dough of the usual stiffness. 
The dough is allowed to stand, not longer than an hour, and at 
times is molded into loaves immediately upon mixing. After 
it has risen to the degree of lightness desired, it is baked in the 
usual way. 



name baking powder covers a wide range of substances 
which are incorporated in a dough to give forth leavening gas 
in the oven. However, the term may now be limited to this 

equation : 

Acid + alkali + water + heat = carbon dioxid -[- neutral 
salt residue. 

Kirkland 1 states that the first mention of baking powder in 
England dates at eighty years ago, as pearlash and alum and 
later as sesqui-carbonate of ammonia. Baron Liebig, the great 
German chemist, and the first man to handle the subject scien- 
tifically, suggested 

Hydrochloric Sodium Carbon Common 

acid bicarbonate Water dioxide salt 

HC1 + NaHCO 3 = H 2 O + CO 2 + NaCl. 

The first patent, by Dr. Whiting in i837, 2 used the above 
formula. Thus, from the beginning, sodium bicarbonate ap- 
pears as the alkali. The subsequent history of baking powder 
manufacture centers in the endeavors to obtain a satisfactory 
substance for the acid. The first decided advance was in the use 
of a solid acid substance. Professor Horsford, of Cambridge, 
Mass., patented his acid phosphate powder in 1864, and inter- 
ested his former teacher, Liebig, in introducing and manufac- 
turing it in Germany. Horsford began to advocate phosphate 
powder in 1861, and Liebig in i869. 3 The Hoaglands, Fort 

1 "The Modern Baker, Confectioner and Caterer," John Kirkland, 
London, 1910; p. 239. 

2 Ibid. 

3 "The Theory and Art of Breadmaking," E. N. Horsford, 1861 ; p. 31. 


Wayne, Indiana, druggists, are said to have originated the cream 
of tartar powder in I868. 1 They founded the Royal Baking 
Powder Company. "Alum" powder appeared about iSSo. 1 The 
acid substance "S. A. S.," which now replaces the alums, dates 
from 1892. The United States, which claims much the largest 
per capita consumption of baking powders, manufactures the 
so-called cream of tartar, phosphate and "alum" powders, ac- 
cording to modifications or combinations of the three following 
general formulas: 

Cream of tartar 

(i) KHC 4 H 4 16 


NaHCO 3 

8 4 


= C0 2 



H 2 


Rochelle salt 

Acid calcium 


(2) 3 CaH 4 (P0 4 ) 2 + 8NaHC0 3 





Normal calcium 

Acid sodium 

= 8C0 2 + 

8H 2 

f- Ca 3 (P0 4 ), 

\- 4Na 2 HPO 4 . 






Basic sodic aluminic sulfate 

(3) aNa 2 SO 4 ,&Al 2 (SO 4 5,,cAl 2 O 8 + dNaHCO 






/H 2 







From the standpoint of the consumer, the ideal baking pow- 
der (a) gives the most gas for the least volume and weight of 
1 "The Baking Powder Controversy," A. C. Morrison, New York, 1904. 


powder ; (b) gives the gas slowly when cold and increasingly in 
the cooking dough; so the dough may be mixed cold and kept 
standing several hours ; begins to generate gas in quantity in the 
oven and ceases to generate when it would rupture the crumb ; 
(c) leaves a tasteless and absolutely harmless residue in the 
bread; (d) is cheap; (e) keeps well. The chemicals should not 
react on one another in the can and thus lose strength. 


It will be noticed that sodium bicarbonate appears in all of 
the foregoing formulas. Th^_ae.rgjhr}g- gas, carhnn Hin^id. comes 
from the reaction of the acid on sodium bicarbonate, which holds 
the field as the alkali substance. 

"Soda" is a white salt with alkaline taste, made chiefly by the 
ammonia-soda process 1 

NaCl + NH 4 HC0 3 = NaHCO 3 + NH 4 C1, 
or the Solvay process 
NaCl + NH 3 + CO 2 + H 2 O = NaHCO 3 + NH 4 C1. 

It gives off CO 2 readily when heated. The resultant Na 2 CO 3 is 
a rank tasting alkali that yellows the bread. For this reason 
"soda," or "saleratus," is not used alone, but is neutralized with 
an acid principle that will leave a palatable salt residue. The 
sodium compounds are mostly inoffensive and neutral in the 
digestive tract. 

Other compounds sometimes used for or with soda are mag- 
nesium, potassium and ammonium carbonates. The addition of 
a small percentage of magnesium carbonate is not uncommon. 
It is cheap, bulks seven times 2 as much as "soda," and is much 

1 "Sulfuric Acid and Alkali," Vol. Ill, p. 15, G. Lunge. 

2 " Baking Powder," F. S. Foot, New York, 1906. 


slower reacting. It supplements the initial reaction of "soda" 
and makes a better keeping powder. Its salts are harmless but 
often unpalatable. Potassium carbonate has been rejected be- 
cause of its bitter residues. Ammonium carbonate can be used 

(NH 4 ) 2 C(X = 2NH 3 + CO 2 -f H 2 O, 

or the sesqui-carbonate, both of which are volatile at oven heat. 
While these two carbonates, when pure, leave no residue, their 
odor is not always driven out of the goods. 


Cream of Tartar. While the alkali has always been sodium 
bicarbonate, many compounds have been used as the acid sub- 
stance. Cost and availability have been variable quantities, and 
aerating value, keeping quality, and the character of the residues 
have been constant quantities, governing the choice of the acid. 
The aerating value is calculated from the molecular weights in 
the reaction, according to the proportion 

100 : X = acid : sodium bicarbonate. 

Tartaric acid (H 2 C 4 H 4 O 6 ) a*nd its acid potassium salt (cream 
of tartar), either or both, form the acid of the tartaric powders 
(Formula i). Crude cream of tartar is deposited as argols in 
wine casks. It is obtained in California, and is imported from 
France, Italy, etc. Cream of tartar (KHC 4 H 4 O 6 ) is present in 
the juice of grapes. Fermentation causes it to crystallize out in 
hard red aggregations, as it is unsoluble in alcohol. These ar- 
gols are purified by double crystallization. One part cream of 
tartar is soluble in 15 parts boiling water, and in 416 parts water 
at o C. 1 The red grape color is taken up by pipe clay or egg 
albumen. Tartaric acid is a by-product in the manufacture of 
1 Encyclopedia Brittariica, Vol. XXI ; p. 43. 


cream of tartar. Tartaric acid, having two acid radicles com- 
pared with one in cream of tartar, will react on more than twice 
the amount of soda in other words its aerating efficiency is 
more than double that of cream of tartar. It is not preferred, 
however, as its reaction is rapid and complete with cold water, 
and its keeping quality correspondingly poor. As high as seven 
per cent, tartaric acid is now used in baking powder, with a gain 
in the aerating value and apparently no loss in the keeping qual- 
ity. Cream of tartar forms the bulk of the acid in its powders, 
with often a small percentage of tartaric acid to give quick 
initial reaction, or with acid calcium phosphate. Efforts have 
been made to make tartaric acid available by coating the crystals 
with egg albumin, melted paraffin, etc. Cream of tartar pow- 
ders are the most expensive, keep well and aerate well. The 
residue, sodium potassium tartrate, plus four molecules of 
water of crystallization, is known as "Rochelle Salts," a mild, 
cooling purgative. This residue is slightly greater in weight than 
the original cream of tartar and the "soda." The residue from 
using tartaric acid is normal sodium tartrate. Cream of tartar 
has an aerating value of 44.7; tartaric acid, 112.0. 

Phosphate. The acid of the phosphate powders is monocalcium 
phosphate (CaH 4 (PO 4 ) 2 ). "Phosphate" is a deliquescent, 
transparent, crystalline substance obtained by the sulfuric acid 
digestion of calcined bones. 

Ca 3 (PO 4 ) 2 + 2H 2 SO 4 = CaH 4 (PO 4 ) 2 + 2CaSO 4 . 

Its principal impurity is calcium sulfate. It has such a strong 
affinity for air moisture that it will not keep unless specially 
treated. Phosphate powders were once sold in two packages, 
keeping the acid separate until mixed in the dough. Coarsely 
granular structure improves the keeping quality. A recent 
method of mixing the liquid phosphate with starch and drying 


the whole is said to be successful. Phosphate is cheaper than 
cream of tartar and reacts favorably in the dough. AJhe residue 
is made up of neutral calcium phosphate which is insoluble, and 
di-sodium hydrogen phosphate with 12 molecules of water of 
crystallization. 1 The latter soluble residue is about three-fifths 
of the weight of the reacting chemicals. This residue is claimed 
to have a positive food value, supplying the phosphoric acid to 
replace that milled out of wheat by the roller process. The 
aerating value of the pure salt is 95.7, according to Formula (2). 

Aluminum Salts. These salts, whose baking powders have 
been called "alum" powders, need a more discriminate naming. 
Alum has the symbol K 2 A1 2 (SO 4 ) 4 , 24H 2 O. The alums are a 
salt group with the general molecular construction M 2 N 2 (SO 4 ) 4 , 
24H 2 O, in which M is sodium, magnesium, caesium or one of 
the other monovalent metals, and N is the trivalent element 
aluminum, or sometimes iron, manganese, etc. The alums are 
of similar symbol, crystallize in the isometric system, and are 
soluble in water. They have an astringent taste. When cal- 
cined, the water of crystallization is driven off and the salt falls 
into a fine powder. Alum and ammonium alum so treated are 
less soluble and astringent and are called "burnt" alums. So- 
dium alum is a possible salt that is not a commercial substance, 
as it is very difficult to crystallize. The alums are made by 
mixing correctly proportioned solutions of the two sulfates and 
allowing the mixture to crystallize. Aluminum sulfate was 
formerly made from cryolite and bauxite. It is now made only 
from bauxite (A1 2 O 3 ). Potassium sulfate is mined in a lacus- 
trine deposit which contains it capping rock salt at Stassfurth, 
Germany. Ammonium sulfate is a by-product from gas and 
coke works. Sodium sulfate is found in the arid districts 
1 ''Qualitative Chemical Analysis," Fresenius ; p. 66. 


of our West, and is obtained as a by-product from the manu- 
facture of hydrochloric acid. 

2NaCl + H 2 SO 4 = 2HC1 + Na 2 SO 4 . 

Alum and ammonium alum were first used in the manufacture 
of alum powders, by manufacturers who bought them under the 
name "C. T. S." (cream-of -tartar substitutes). The powders 
made from "C. T. S." were strictly alum powders, and might 
be illegal in certain territories. In 1892 the basic sodic aluminic 
sulfate, "S. A. $.," was evolved. This substance, either alone or 
combined, with phosphate or tartaric acid, is now used to the ex- 
. elusion of the alums. As noted in Formula (3) the symbol of the 
latter salt calls for indefinite amounts of the two sulfates and 
for an excess of aluminum in the form of oxid. One analysis 
of the compound shows it to contain 70^/2 per cent, aluminum, 
and 27^4 per cent, sodium sulfates. 1 This makes no allowance 
for A1 2 O 3 . For the reason that sodium sulfate forms a bitter 
residue the proportion of it is cut low. This compound has an 
aerating value of about the same as tartaric acid, has first class 
keeping quality, and is nearly tasteless. 

This basic sodic aluminic sulfate is made as follows : Nitre 
cake (Na 2 SO 4 ) is dissolved in water and the arsenic is pre- 
cipitated with a sulfid. The solution is filtered and boiled down 
with bauxite (A1 2 O (OH ) 4 ), filtered again and evaporated until the 
salt begins to crystallize out. The thin cakes of the salt are then 
calcined to nearly red heat (560 C.) in a revolving steel drum. 
This substance has no fixed symbol and is in no sense an alum. 

Supposing that the pure soda were mixed with the pure acid 

substance so as to exactly neutralize, the following percentage 

weights of carbon dioxid would be obtained : cream of tartar 

1 6. 2, tartaric acid 27.6, basic aluminic sulfate 30.6, ammonium 

1 Gilbert L. Bailey, Los Angeles, 1911. 


alum 33.7, calcium phosphate 25.6; ammonium carbonate alone 
63.5 ; tartaric acid and magnesia 14.5. 


The starch of baking powder is not only not a filler or adul- 
terant it is necessary in most climates to keep the acid and alkali 
from a too intimate contact, and to absorb the moisture of either. 
Flours, potato and other starches are inferior to corn starch 
of commerce, which should be of neutral reaction and dried 
from normal 13-18 per cent, to not less than five of moisture. 
Starch is used in percentages of 10-50 per cent. Only when used 
in excess or when made up with inferior starch, talc or "terra 
alba" (gypsum) is starch objectionable. As with other food 
products adulteration would not pay even temporarily except 
through misleading advertising. The alum powders of 1889* 
were notably low in aerating value and high in starch. The pres- 
ent aerating value of all good modern baking powders is approx- 
imately the same. 


Eleven per cent, by weight is a normal amount of "available" 
carbon dioxid. 2 Deterioration may bring this down below 2 
per cent, of weight. As before intimated it is quite as important 
that the powder give off gas according as it is needed in the 
dough, not too readily when cold and not at all after the crumb 
begins to form. The full evolution represents the "available," 
not the total carbon dioxid. Different flours and forms of cake 
and bread need specially balanced powders. 

Egg albumin is used to some extent to increase the efficiency 
of the CO 2 evolved. The albumen, which is very retentive of 
the gas, reinforces the same property of the gluten of flour. 

1 U. S. Dept. Agr., Div. of Chem. Bulletin 13, Part V, 1889. 

2 Foot gives 14 per cent., or 50 times its volume of gas. 



a b 

> rt 

I I 


S o* 




CO - . 10 

: ; 



C 10 M 

: : 







CO ^ l^ O 
(S CO ' ' ' -i C4 

: : 



O O to to O ^ 
OOt~^I IrO>O IrOt^ 

M CO - 



IO t^. ' t^. M . 

C* Q >.- M M 


o o >o o o Tf 




CO rf . . cs <N . CTNOO' 




*:.:':': 8?: 

; ; 


10 O O O O> 

10 * 



ovd . c^ao' . . . <N 

to t^ 





* * 

T , 

10 10 o M 

rf ^ 


cox) 6 ... . . M 

(N HH 10 M 

CO 10 




10 o 10 



10 to 10 r>. 

co O 


<N W VO M 

10 T 




r^ O O co ... 




10 co co 


r>. fx 10 . . . . . I 

es M 10 

:::::: : : : o" 

* (3 

*ja ^ 


It: Hill 




S rt'^3 




tj 53 

c3 .o 

Pn 'w 



t+H .^ 

Z O o3 


TJ bjo ^ 

II . 

H^ . C _, 

: t> < 5 


In warm climates all food stuffs deteriorate more rapidly than 
elsewhere. The length of time required for proper yeast fer- 
mentation as well as the more perishable nature of foods pre- 
pared with it and inability of yeast to raise dough rich in eggs, 
butter, etc., led to the present day widespread use of baking 
powders. Such powders act at once, the gas therefrom raising 
the dough purely mechanically without any alteration or semi- 
digestion of ^he flour, as is the case when yeast is used. .Foods 
raised with baking powder may be safely used hot from the 
oven, in fact most of them are so used. 


A test to determine whether the hard or soft wheat flours 
were better for baking powder biscuits was carried out in the 
Macdonald Institute, Guelph, Ontario. 1 The flours were two 
high patent Manitoba, a nearly straight Ontario, a 20-80 blend 
of a Manitoba high patent and the straight Ontario, and two soft 
Ontarios, 85 and 35 per cent, respectively. The flours were sub- 
jected to a uniform baking test; the recipe called for 300 grams 
flour, 24 butter, 16 baking powder, (kind not stated) 218-252 
milk (the Manitoba patents taking the most milk) and an oven 
temperature of 232 C. The judges were a committee of three 
members of the Dominion Millers' district meeting. 

The conclusions were that the soft Ontario flours made the 
best handling dough and the tenderest and cheapest biscuits. 


All baking powders are naturally in a' measure perishable, de- 
teriorating by reason of the gradual loss of gas available. The 
various powders vary in keeping qualities, those containing alum- 
inic sulfate being the more durable, stronger and much less ex- 

1 Thirty-fourth Annual Report of the Ontario Agricultural College, 1908. 


Any and all baking powders should be kept away from moist- 
ure andheat. Thej- should be kept tightly sealed! Nothing 
should be added to or used in connection with baking powder, of 
an acid or alkali nature, in any such quantity as to disturb the 
nice chemical balance existing between these two elements in any 
well made powder. Baking soda, which is the same as saleratus, 
also sour milk or fermenting molasses, are the materials most 
likely to be improperly added in this way. If the baking powder 
is known to be quite old and must be used notwithstanding age, 
the use of some sour milk or fermenting molasses in the water, 
or sweet milk employed to mix the flour with, may restore some 
of the probably missing acid strength needed to release the gas. 
(See under "Analysis" for easy method testing for excess alkali). 
Grocers are especially warned by manufacturers not to place new 
food stuffs in front of old on their shelves but to sell off senior 
goods first. 


Some of the relatively successful substitutes for a good baking 
powder are : 

Sodium bicarbonate alone. Its residue, Na 2 CO 3 gives the bread 
a rank taste and yellow color. 

Ammonium carbonate, (NHJ 2 CO 3 , ("volatile"). It has six 
times the aerating value of an aluminic powder. Ammonium 
carbonate was once under the prejudice of its source of manu- 
facture. However, it is now made from coal. Unless the bread 
is in small sizes all of the salt is not driven off and the taste and 
smell remain. 

Baking soda and sour milk. Here the lactic acid of the milk 
neutralizes the soda. Such a mixture must always be by guess, 
and it is not possible to neutralize sufficient soda with the dilute 
milk acid.y- 


Baking soda and old fermenting, or "working" molasses. Con- 
siderable skill is required to judge of the necessary proportions. 

Beating up graham or whole dough and baking quickly in cast 
iron pans gives a fair bread. 1 

Making up a stiff dough with snow crystals. 1 

Beating eggs into the dough. 1 

Using the volatile property of alcohol by mixing in wine or 
brandy. 1 


The first requirement of a baking powder, of course, is that its 
reaction in the dough, and its residues, shall be harmless to the 
consumer. If the "baking powder controversy" was of special 
value to the world it was in showing that there is no record as 
yet of injurious result from using any baking powder well made 
by any of the standard formulas. In a baking powder it is not a 
question of whether "alum" is harmful or phosphate and cream 
of tartar wholesome, but of whether their residues in bread are 
deleterious. Using the three primary powders according to 
recipe, one would have to eat the following number of biscuits 
to take a dose of their residual salts. 2 


Cream of Tartar 48-96 

Phosphates 120-240 

Alum 80-160 

The baker and housewife must bear in mind that when a good 
baking powder is mixed in the dough, it will be a different sub- 
stance in the baked bread. " Neither "alum," phosphate nor cream 
of tartar will remain. 

1 "Sanitary and Applied Chemistry," L. H. Bailey, New York, 1906; 

P- 155- 

2 (U. S. and National Dispensatories). " Baking Powder," F. N. Foot, 
New York, 1906. 



Kirkland 1 mentions lead being found in some English creaim 
of tartar. Sul fates may contain small quantities of arsenic. 

It seems to be taken for granted that the chemicals of the dif- 
ferent powders do not react on the dough substance. Hence in 
graham and whole-wheat flours baking powders may be used to 
avoid the degrading action of the flour enzymes during fermenta- 
tion; or in doughs rich in eggs, butter, etc., in which yeast will 
not act. A self-rising flour is one which contains a baking 
powder mixture, usually a phosphate. 


The manufacturing unit consists of receiving bins, drying and 
grinding apparatus, sieves and a mixer. In the larger factories 
automatic scales, conveyors, packing machines are necessary. It 
is to be supposed that the ingredients will vary in purity and 
hence in reactive value, from time to time ; and this will suggest 
that the amounts by weight of the ingredients must vary and that 
quantitative tests should play an important part in careful manu- 
facture. Ingredients are tested before mixing for purity and for 
dangerous impurities, and after mixing for aerating value and 
keeping quality. A double system of checking the mix day by 
day will prevent malmixtures getting beyond the factory. It is 
said that businesses have been ruined by marketing one wrongly 
made up batch of baking powder. 

'Besides comparative purity of the chemicals, it is necessary 
that they be well dried. The starch is dried to about 8 or 9 
per cent, of moisture. Phosphate should be protected from 
moisture. Care in drying the soda prevents its gas being driven 
off. To prevent intimate contact all but the starch are better in 
a granular state especially the phosphate and tartaric acid. 
As noted before, an artificial coating of paraffin, albumin, starch, 
1 Vol. I, p. 241. 


etc,, is sometimes added to the acid ingredient. Finally the 
powders are packed in tins, practically air and moisture proof 
a decided improvement over the paper package. 


Baking powder analysis falls under two heads : ( i ) The manu- 
facturer's tests of his ingredients for percentage of purity, free- 
dom from dangerous impurities and his analysis of the finished 
powder for mistakes in mixing, for available carbon dioxid and 
keeping quality; (2) The food chemist's (government) tests 
for freedom from adulterants, poisons, and for available carbon 

Adulterating with terra alba or excess starch or flour would 
not pay as it markedly decreases the strength of the powder. 
The ingredients coming to the manufacturer do not purport to be 
chemically pure, but contain small quantities of unimportant 
iron, magnesium, calcium and sodium salts. Arsenic is an oc- 
casional impurity in sulfates. 

Mistakes in mixing may be easily caught, independent of the 
check' sheets, by dissolving the powder in pure water, boiling to 
make a complete reaction and testing for marked excess acid or 
alkali with litmus paper. An exact mixture gives a purple color, 
which becomes red in excess acid and blue in excess alkali. The- 
oretically the baking powder is so mixed that the acid and alkali 
shall exactly neutralize each other. Actually, however, tartrate 
powders give a slightly acid end reaction and other powders an 
alkaline reaction. The accuracy of the mixing is tested as fol- 
lows : One grain of the powder is boiled for several minutes, the 
solution made acid with five cc. of tenth normal sulfuric acid, 
then titrated with tenth normal sodium hydroxide. The indica- 
tor is phenolphthalein. A correct alkaline powder will require 
about 4.5 cc. of the hydroxide solution. 


Keeping quality is tested briefly as follows i 1 

A given weight of powder is first analyzed for total CCX; is 
then spread on watch glasses and exposed to the air for a stated 
time. The difference between total CO 2 before and after the ex- 
posure indicates the keeping quality under extreme conditions. 
To approximate an extreme long-time test, the watch glasses of 
the powder are set for a stated time in a covered bell jar, in 
the bottom of which is a dish of water. For determination of 
free and total tartaric acid, cream of tartar, phosphoric acid, am- 
monia, starch, etc., see Bulletin 107, (1907) Bureau of Chemistry, 
U. S. D. A. 

Available CO 2 is the difference between total CO 2 and resi- 
dual CO 2 . 

Available CO 2 : Total CO 2 = x : 100 is determined as fol- 
lows i 1 

"Weigh two grams of baking powder into a flask suitable for 
the subsequent determination of carbonic acid, add 20 cc. cold 
water, and allow to stand 20 minutes. Place the flask in a metal 
drying cell surrounded by boiling water and heat, with occasional 
shaking, for 20 minutes." 

"To complete the reaction and drive off the least trace of gas 
from the scum and solid mass, heat quickly and boil one minute, 
aspirate until the air in flask is thoroughly changed and determine 
the residual CO 2 by absorption, as described." 

Knorr's method 2 for total CO 2 is as follows : 

"Place some of the baking powder in a perfectly dry distilling 
flask (Fig. ii ). Close the flask with a stopper carrying the 
tube connecting with the absorption apparatus and also with the 

1 "Baking Powders," C. A. Catlin, Providence, 1899; p. 23. 

2 "Methods of Analysis;" U. S. Dept. Agr., Bur. of Chem., Bulletin 
107 ; pp. 169-178. 



funnel tube. Weigh the tubes in which the carbon dioxid is to be 
absorbed and attach them to the apparatus. In case two Liebig 
bulbs are employed, one for potassium hydroxid (1.27 or 1.55) 
and the other for sulfuric acid to absorb the moisture given up 
by the potassium hydroxid solution, weigh them separately. If 
two soda-lime tubes are employed, it will be found advantageous 

Fig. ii. Knorr's apparatus for the determination of CO 2 . A Distilling flask fitted to 
condenser by a ground-glass stopper; B Reservoir containing acid; C Soda-lime 
tube fitted to acid reservoir by a ground-glass stopper; D Condenser; E Liebig 
bulb with a solution of KOH for the absorption of CO 2 and followed by a CaCl tube. 
An additional guard tube filled with soda lime should follow the tube F, though not 
shown in the cut. From U. S. D. A., Bur. of Chem., Bull. 107. 

to weigh them separately and fill the first tube anew when the 
second tube begins to increase in weight materially. Nearly fill 
the tube B with hydrochloric acid (sp. gr. i.i) and place the 
guard tube C in position. Then start the aspirator at such a 
rate that the air passes through the Liebig bulb at about the rate 
of two bubbles per second. Open the stopper of the funnel and 
allow the acid to run slowly into the flask, care being taken that 


the evolution of gas shall be so gradual as not to materially in- 
crease the current through the Liebig bulb. After all the acid 
has been introduced continue the aspiration and gradually heat 
the contents of the flask to boiling, the bulb in tube being closed. 
While the flask is being heated the aspirator tube may be re- 
moved, although many analysts prefer, when using ground glass 
joints, to aspirate during the entire operation. Continue the boil- 
ing for a few minutes after the water has begun to condense in 
D, then remove the flame, open the valve in the tube B, and allow 
the apparatus to cool with continued aspiration. Remove the 
absorption tubes and weigh. The increase in weight is due to 
carbon dioxid." 


Baking powders are more generally used in this country than 
elsewhere, and more in the South than in the North. The 
bulk of the powders are aluminic powders, used in the South 
especially. Cream of tartar powders are confined largely to the 
North and the Pacific coast. The following figures are taken 
from the Memorial of the American Baking Powder Association 
presented in Congress in 

Tons used per annum 

Manufacturing concerns 


524 (Alum and alum phosphate) 

Cream of tartar 

The Royal Baking Powder_Company- (trust) was organized 
in 1899, from the three leading cream of tartar baking powder 
companies, and the two largest importers of argols. The capital 

stock is $20,000,000, half of which is preferred. It is claimed 
.to have a monopoly of the imports of argols. The cream of 

1 ''The Baking Powder Controversy," A. C. Morrison, New York, 1904; 
Vol. I, p. 54- 


tartar interests have long been waging an aggressive war on all 
powders containing so-called "alum." To meet this aggression 
the majority of the alum baking powder manufacturers formed 
the American Baking Powder Association. The cheapness and 
availability of the aluminic substance made a rival monopoly 
impossible. This defense Association has successfully warded 
off prohibitory "pure food" legislation and carried on a cam- 
paign of education as to the true nature of aluminic powders. 
The records of this warfare have been published by^the Asso- 
ciation in two large volumes. 


The first aerated bread patent was taken out in England in 
1832 by Luke Wright. In 1856 Dr. John Dauglish brought forth 
the process which bears his name. He made bread by mixing 
flour, and water charged with carbon dioxid under pressure. 
The releasing of the dough in the pans and the heat of the oven 
expanded the gas in solution and raised the dough. Thus he 
obtained bread without yeast or fermentation: The primary 
claims of Dr. Dauglish for his process were that by doing away 
with the process of fermentation his bread was cheaper and 
more nutritious. Both his method and the present American 
method will be here described, more because of their interest 
and possibilities than because of economic success. 

The English method of a quarter of a century ago was de- 
scribed in Industries 1 at that time. Carbonic acid was made up 
to a pressure of 40 pounds ; the carbon dioxid was made by dis- 
solving chalk in sulfuric acid and passing it through lime, and 
was stored in India rubber bags. The mixer was a cast iron 
vessel, enamel lined. The flour was measured in, the "soda 
water" turned in, the trap closed and the dough made up under 40 
pounds pressure by the churning of the mixing arms. "The bot- 
tom of oach mixer is provided with several holes, closed by 
special valves termed 'dough cocks.' These are so arranged that 
when the handle is turned around, the hollow plug of the cock 
takes out sufficient dough to speedily expand into a loaf of the 
shape of the tin *'*''*,..' Enameled surfaces and asbestos 
packed valves kept the dough clean throughout. In 1886 the 
London Aerated Bread Company made up weekly 1,000 sacks of 
flour by this process. Flavor, color and texture were brought up 
1 Scientific American Supplement, Sept. 25, 1886. 


to the necessary high standard for success by using considerable 
malt or "wine" in the recipe, according to the Childs process. 

Aerated bread has been made in Germany and France. It 
is still made to a limited extent in England by one company 1 and 

Wxfag. ~ 

Fig. 12. Aerated bread machine. (Courtesy Meek-Barnes Baking Co., I v os Angeles.) 

in America by one company. In this country Mr. Withington 
of Cincinnati, appears to have been the pioneer. He and Mr. 
Kohlsaat introduced it in Chicago about 1885, and later Mr. 
Withington went to Boston and made it there. Mr. Kohlsaat 
1 Courtesy of The British Baker, London. 


stated that his concern was doing a flourishing business with 
this bread, selling it in wagons decorated with red banners. 
During the Haymarket riot the banners were changed to blue. 
It was a financial success and was liked by his customers, though 
it did not keep well. At present it appears to be made only in 
Los Angeles. The following description is given through the 
courtesy of the Meek-Barnes Baking Co., of Los Angeles. 

Fig- I 3- Carbon dioxid attachment for aerated bread apparatus. 

The mixer (Fig. 12) is a double cast sphere a yard in diame- 
ter and three-quarters of an inch thick set five feet above the 
floor by a trussed frame. The mixing sphere contains the mix- 
ing arms mounted on a diametrically placed axle which is geared 
on the left side to the counter shaft mounted under the back of 
the mixer. 


The mixer sphere has a main charging trap on top which is 
shown with a funnel. When charged the funnel is taken out, 
a rubber disc placed over the hole, and then a cast iron disc 
which is held down by the socketed lever. 

The carbon dioxid is introduced as gas through a pipe into 
the top. Fig. 13 shows how the. carbon dioxid cylinders are con- 
nected to a receiving drum which allows the gas to warm as it 
expands. It is released from this drum through a reduction 
valve carrying a pressure gauge. By connecting two cylinders 
to the single receiving drum one cylinder can be used to supply 
the first gas at low pressure while the newer cylinder is reserved 
to carry the final pressure to 200 pounds. 

The mixer sphere has a small blow-off valve above, while in 
the bottom is the dough cock. It will be noticed that all the 
packed joints have a wide bearing, so as to dispense with oil and 
yet prevent leakage. 

The operator, having thoroughly cleaned the machine, charges 
the weighed flour, salt and lard through the trap, and lets in 
water to make a thin dough, nearly filling the mixer. He starts 
the motor and mixes the batch for one-half hour and then judges 
if the dough is of correct consistency. The top trap is now 
clamped down over the rubber seal, and carbon dioxid is let in 
at 100 pounds pressure, The mixing continues for 20 min- 
utes longer, the gas pressure running up to 200 pounds. Both 
power and gas are now turned off.. The assistant keeps a stack 
of empty pans at the left of the operator, who puts one after 
the other beneath the outlet, turns the cock and lets out a half 
pan of dough and places the pan on the long peel at his right. 
The assistant removes the peels and charges the oven prefer- 
ably a reel. As the pressure drops from withdrawing the con- 
tents, the mixer sphere may be recharged toward the last. 


The dough shoots out of the discharge valve with a "cough;" 
it takes practice to fill the pans evenly. The dough begins to 
swell at once. The baking takes 40 minutes. The loaf has a 
rough, irregular top crust, browned in patches and without 
bloom. The crumb is fine, very even and a very good white. 

This apparatus takes two men one of them skilled, turns 
out a batch of 185 two-pound loaves every two hours, calls for 
power from a two horse-power motor half the time, and exhausts 
a large carbon dioxid cylinder about every five batches. It will 
be noticed that compared with the old English "soda water" 
apparatus, the tanked carbon dioxid is a great convenience. 

The advantages claimed for this process are: 

(i) A great saving in labor, time and yeast; (2) there is 
no fermentation change or loss in the dough; (3) the entire 
process is cleanly, neither handling nor standing of the dough 
being necessary; (4) the bread is more nutritious and whole- 
some, not having been fermented; (5) the bread has a white 
crum and good flavor. 

There is no denying the force of the first three arguments. 
However, it was soon found that the original bread with its un- 
fermented gluten had a raw taste and would not hold the market. 
The addition of malt extract, etc., to the mix made a much more 
palatable loaf, whiter and of better texture. This made it a 
success in England thirty years ago, but defeated the contention 
that yeast was a harmful leavener. The "wine" or malt per- 
formed the work of the fermentation products. The claim of 
Dr. Dauglish that yeast fermentation causes a loss of 6 per cent, 
of the dough substance is extravagant. Jago says it is not more 
than 2^2 per cent. Other recent authorities put it as less than 
i per cent. This loss is of course avoided in this process. The 
real value of the process would seem to be in its ability to make 


sound bread from flour high in bran, flour enzymes and germ 
substances. Mr. Kohlsaat speaks well of the flavor of aerated 
bread, and its advertising possibilities, but says that it did not 
keep. The conclusion is that experimenting may bring this 
process forward again as a cheap, very quick and cleanly process 
for large bakeries. Both the flavor and the appearance of the 
top crust should be improved on. 


"The first account of powdered milk is found in Marco Polo's 
report of his travels in Tartary in the interior of Asia. In about 
1290 he found the Tartars drying milk in the sun, pulverizing 
it into powder and placing it in sacks to be carried on their ex- 
cursions into the territory of their enemies." 2 Powdered milk 
was again heard of in England about -100 years ago. It has 
recently come to the front very prominently in this country. 

It is quite likely that wholesale milk users will in time use milk 
powder to the exclusion of the original liquid. 

The following table gives average analyses for liquid and dried 
whole milk : 



powder 4 


i 60 


'4-o u 

2 80 

5i' Z(J 

o9"' u 


420 I 



O 7"\ 

6 o 

** /O 


Per cent of solids 

12 2^ 

Q 7 A 

<J. 1^ 

To reduce milk to a powder, the water must be evaporated 
off in such a manner as not to chemically alter these susbtances, 
and to leave a powder that is again soluble in water to the con- 

1 Much of the data for this chapter was obtained through the courtesy 
of Lewis C. Merrell, of Merrell-Soule Co. 

2 Technical World. 

8 Anal. Milt. Milchw. Ver. Allgaie., 21, 1910. 

4 " Economic Reasons for the Reduction of Milk to Powder," Lewis C. 
Merrell, Journal of Industrial and Engineering Chemistry, Aug., 1910. 


sistency of milk. The difficulties that may arise in the stages of 
the process are : 

(1) Coagulation of the albumen above 149 F. 

(2) Browning, or caramelizing, of the milk sugar much above 
212 F. 

(3) Breaking down of the butter fat globules by heat. This 
destroys the emulsifying power of the powder and would pre- 
vent cream and whole milk from being dried. 

(4) Between the percentages of 40 to 10 per cent of water 
the milk becomes a sticky paste, hard to dry or handle. 

(5) In any slow drying process the lactic acid content is rap- 
idly increased, and this acid begins to act on the milk solids. 

Milk can be successfully reduced to powder by removing a 
portion of its water by agitation in a vacuum pan ; the boiling is 
thus carried on at a temperature below the coagulation point of 
albumen. This condensed milk is then sprayed into a current of 
hot air. This reduces the moisture to less than three per cent. 
It is then sterile to the lactic acid bacteria, and can be kept in- 
definitely. The albumen has not been cooked and the butter 
fat has not been broken down, because the rapid evaporation 
of the milk spray reduces the temperature of each spray drop 
until dry. The pasty stage (between 10 to 40 per cent, water) 
has been passed while in the air in a finely divided state. Lewis 
C. Merrell estimates that each pint of milk has a spray surface' 
of two acres. 1 

In a French process, patented in 1910 by Lecomte and Lain- 
ville, 2 the milk is first frozen to a snow powder ; the soft, greasy 
milk solids are separated from the snow by centrifugal action, 
and then dried. This snow residue, however, must contain a 

1 " Economic Reasons for the Reduction of Milk to Powder," Lewis C. 
Merrell, Journal of Industrial Engineering and Chemistry, Aug., 1909. 

2 Scientific American, Nov. 12, 1910. 


large percentage of solid residue; such a process would be 

One pound of dry milk powder is the equivalent of about 
seven pounds of cream or n pounds of skimmed milk. 

Summary of advantages of milk powder: 

(1) It keeps an indefinite time. Two-thirds the annual milk 
supply comes between April and September, while great areas 
of potential dairy lands are too far removed from market for 
liquid milk. Hence both producer and consumer become inde- 
pendent of these two limitations. The milk of any region and 
any period of time can be made up for a steady market. 

(2) The ratio of freight charges on liquid and dry milk 
are about as 14 to one. You do not have to pay freight on the 
water; also, the advantages of easy handling and stability bring 
a lower proportional rate to the dry milk. 

(3) The retail price is on an average with liquid milk. The 
cost of the process is about neutralized by the reduced freight. 

(4) Milk powder bulks about one-eighth of liquid milk. 

(5) It is easier and safer to handle all along the line. 

(6) Milk powder can be bought and sold on an accurate 
guarantee of composition and purity. 

Its present market is among the large bakeries, confectioners 
and the government, and occasionally as a filler in baking 

It is sold as cream, whole milk and skimmed milk powders. 
Bakers may mix the powder with their flour before adding wa- 
ter; but it is recommended to dissolve the powder first and use 
it as liquid milk. 


Milk powder is at present made in the States of California, 
Illinois, Iowa, Michigan, New Jersey and New York. The 
State Dairy Bureau of California reports a yearly output of 
about 600 tons, less than one per cent, of the total milk. 1 There 
appear to be three companies at present doing business in the 
United States. 

1 Courtesy of F. W. Andreasen, Secy. 


Acetic acid, effect on yeast 6 

in bread 40 

Acidity of bread 4 

Acid sodium phosphate in baking powder formula 50 

residue 56 

Adulteration, of baking powder 64 

yeast 16 

Aerated bread, advantages of 73 

first patents 69 

flavored by Childs' process 70 

future of 74 

in America -7O-73 

in England 69, 70, 73 

in France 7 

in Germany 70 

manufacture 73 

mixer and apparatus 7 1 

old English method 69 

time of baking 73 

Aeration process, for yeast 22, 33-35 

material for 34 

Albumin, as yeast food 8 

egg, for baking powder 58, 63 

egg, for phosphate 63 

egg, for tartaric acid 55, 63 

yeast 6 

Albuminoids, as yeast food 8 

defined 1 1 

Alchemy and yeast i, 2 

Alcohol, and Basil Valentine I 

aeration process, yield 22 

Vienna process, yield 22, 31 

from fermentation of sugar 15 

in yeast excretions 7 

substitute for baking powder 61 

Alcohols, higher 3, 10 

Alum, true 56 

ammonium 57 

in leading baking powders 59 

Alums, general symbol of 56 

manufacture of 56 

qualities of 56 



Alum baking powder 51 

aerating value of 58 

controversy 68 

composition 59 

first patent 51 

formula 52 

keeping quality 59 

in the South 67 

present output 67 

residue in bread 62 

Aluminum, hydroxid 52 

Aluminum oxid 52 

Amids as yeast foods 8, 41 

Ammonia-soda process 53 

Ammonia determination in baking powder 65 

Ammonium carbonate, aerating value 58, 61 

in baking powder 51, 53, 54 

odor in bread 54 

substitute for baking powder 61 

source of 61 

Ammonium sulf ate 56 

Ammonium tartrate 8 

Analysis, of average milk powder 75 

baking powder 64 

yeast 6, 7, 20 

Argols, cream of tartar manufacture 54 

importers of 67 

Ash, barley and malt 10 

yeast 7, 8 

Attenuating power of yeast 15 

Auto-fermentation of yeast 6, 29 

"Baker's Helper," home-made yeast 45 

Bacteria in yeast 16 

Baking powder, the acid 54 

action on the dough 60 

adulteration 64 

addition of soda, etc., to 61 

advantages of 63 

the alkali 53 

alum 67 

analysis 64 

care of . .60 

INDEX 8 1 

Baking powder continued PAGE 

composition of leading 59 

cream of tartar 67 

deterioration 60 

first patents 51 

formulas 5 2 > 59 

general formula of 51 

history of 51 

ideal 52 

in flour , 60, 62 

in North and South 67 

in warm climate 60 

leavening values 59 

litmus test for 64 

manufacture of 63, 64 

packing in tins 64 

phosphate 67 

restoring old , 61 

starch in : . 58 

substitutes for 61 

tests for 60 

tests in manufacturing 63, 64 

war 68 

Baking Powder Association 67, 68 

Baking test for baking powder 60 

Barley, average composition 10 

Barm , 36, 43 

Basil Valentine and fermentation I 

Beets in yeast mash 22 

Birnbaum, alcohol in bread 40 

Biscuits, baking powder residues 62 

Bottom yeast (see brewers' yeast) 3 

Boutreaux, on French leaven 43 

Bread, flavor from yeast 41 

from bottom yeast 3 

loss from fermentation 40, 42 

yeast action in 36-43 

Breweries and pure culture systems 16 

Brewers' yeasts 3 

Brown, A. J., and Pasteur 2 

laboratory test for yeast 20 

Buchner, isolates zymase 2 



Budding of yeast i 

in nutrient solution 5 

rate of reproduction 5 

Butyric acid, effect on yeast 6 

in bread 41 

Cane sugar, symbol and qualities 1 1 

in yeast mash 22 

Carbohydrates, in bread 39-43 

in barley and malt 10 

as yeast food 8 

Carbon dioxid, "available," in baking powder 58, 59 

in aerated bread 69 

in aerated bread, method of generating 69, 72 

in baking powder formula 52, 57 

from fermentation 10, 15 

in yeast excretions 7 

Cellulose in barley and malt 10 

Centrifugal separation, of milk 76 

of yeast and wort 33 

Childs' process for aerated bread 70 

Compressed yeast, long-distance shipment 45 

Corn, in aeration process 34 

in Vienna process 26 

in yeast mash : 14, 26 

Cream of tartar, aerating value 55, 58 

in baking powder formula 52 

determination of 65 

how formed 54 

in leading baking powders 59 

manufacture 54 

Cream of tar baking powder, composition of 59 

formula 52 

in the North 67 

originated 52 

present output 67 

"C. T. S.," legality of 57 

Dauglish, Dr. John, aerated bread 67 

loss of bread substance 42, 73 

de Latour, vegetable nature of yeast I 

Dextrin, in panification 39-43 

symbol and qualities 1 1-14 


Diastase, production and qualities n, 14 

action in mash 26 

"Diseases" of beer 15 

Dough, and sponge methods 36 

growth of yeast in 42 

Dry milk (see milk powder) 75 

Dry yeast cakes 16 

Eggs, beaten, a baking powder substitute 62 

Ehrlich, on fermentation products IO 

Endotryhtase, isolated by Hahn 9 

Enzymes, action on flour 41 

definition 9 

flour 63 

proteolytic 9 

yeast 15 

Enzymic reactions in yeastmaking 12, 14 

Eethyl alcohol from fermentation 10 

Fehling, loss of bread substance 42 

Fermentation, defined and described -. . . . 15 

disturbances .' 4 33, 35 

formula for mash 14 

in bread 37-43 

Fermentative power of yeast '. 15 

Flavor of bread 41, 43 

Flour, and bread, composition 38 

before and after fermentation 38 

Foam in yeast manufacture 29, 31 

Gay-Lussac, on fermentation 8 

Girard, on yeast in bread 39 

Glycerin, from fermentation 10 

in yeast excretions 3, 7 

Glucose, symbol and qualities 12 

fermentation of 14 

Graeger, loss of bread substance 42 

Graham flour, baking powder 63 

Hahn, and endotryhtase 9 

Hansen, and pure culture 15 

Heeren, loss of bread substance 42 

Higher alcohols, flavor of bread 41 

Hoaglands, cream of tartar baking powder 51 



Hops 43 

Horsford, Prof., and phosphate baking powder 51 

Hydration formula for yeast mash 14 

Inversion formula for yeast mash 14 

Invertase, action on cane sugar 12 

yeast 15 

Jago, loss of bread substance 42 

home-made yeast 44 

on "baker's sourness" 40 

on stages of panary fermentation 37 

Kirkland, first mention of baking powder 51 

lead in cream of tartar 63 

on "virgin barm" 44 

Knorr's test for carbon dioxid 65 

Kohlsaat, Mr., aerated bread in Chicago 70, 74 

estimation of aerated bread 74 

Kohman, conclusions on salt-rising fermentation 50 

experiments with salt-rising bacteria 49 

experiments on salt-rising bacteria 47, 48 

Kuetzing, vegetable nature of yeast i 

Lactic acid, for baking powder 61 

in Vienna process 26 

Lactic acid bacteria, in aeration process 34 

in barm 43 

effect on yeast 6 

Laf ar, definition of fermentation 15 

Lead in cream of tartar 63 

Leaven 43-46 

Le Comte and Lainville, milk powder 76 

Leeuwenhoeck, discovers yeast I 

Levulose, symbol and qualities 14 

Liebig, chemical theory of fermentation 2 

on baking powder 51 

Lindet, on yeast in dough 42 

Litmus test for baking powder 64 

Long-distance shipment of yeast 17-20 

Maercher and Pederson 4 

Magnesium carbonate in baking powder 53 

Magnesium phosphate in yeast ash 7 



Malt, average composition 10 

defined 10 

digestion of in its albuminoids 9 

in aeration process 34 

in Vienna process 26 

in yeastmaker's mash 14, 26, 34 

Maltase, action on maltose 1 1, 15 

Maltose, and dextrin in yeast mash 14 

evolution of in mash 26 

Manufacture, aerated bread 7 2 

baking powder : 63 

compressed yeast 21 

milk powder 76 

salt-rising yeast 49 

Manufacturers' yeast test 20 

Marco Polo, first mention of milk powder 75 

Mash, defined 10 

for aeration process 22 

for Vienna process 22 

yeast makers 14 

Mass action in yeast ' manufacture 13 

Meek-Barnes Baking Co 71 

Merrell, L. C., on milk powder 76 

Metzler, A., test for yeast 20, 21 

Meyer, on yeast 2 

Milk, analysis of 75 

Milk powder, advantages 77 

analysis 75 

bulk 77 

difficulties in making 76 

manufacture 76 

present output 78 

uses for 77 

Mineral matter as yeast food 8 

Mixer for aerated bread 71 

Molasses, in yeast mash 22 

baking powder substitute 62 

Monocalcium phosphate, aerating value 56 

liquid 55 

in leading baking powders 59 

in phosphate powders 55, 63 

Mother yeast (seed yeast) 26, 28, 34 

Mouf ang, on washing yeast 17 



Mycoderma in yeast 35 

Normal calcium phosphate, aerating value 58 

in baking powder formula 52 

coated with egg albumin 63 

in leading baking powders 59 

residue 56 

in yeast ash 7 

Normal sodium tartrate, residue in baking powder. 55 

Oven for aerated bread 72 

Oxygen, relation to fermentation 8 

Pasteur, "Etude sur la Biere" 2 

budding of yeast 5 

growing yeast 8, 15 

pure yeast 16 

theory of fermentation 2 

Peptones, as yeast food 8 

"Philosopher's stone" i 

Phosphate baking powder, aerating value 54, 59 

composition 59 

first patent on 51 

formula for 52 

present output 67 

residue 62 

self -rising flour 63 

in two packages 55 

Phosphoric acid, determination of 65 

in baking powder 59 

yeast washed in 17 

Pohl, alcohol in dough 40 

Potassium carbonate in baking powder 53 

Potassium phosphate in yeast ash 7 

Potassium sulf ate, source of 56 

Potatoes for yeast 43 

in yeast mash 22 

Power for aerated bread making 73 

Proteins in yeast 6 

Proteolytic, enzymes 9 

reaction in yeast mash 14 

Pure-culture lactic acid bacteria 26 

Pure-culture yeast 16 



Reactions of yeast in bread 39~4 2 

Rees, Dr. Max, definition of yeast 2 

Rohrer, Mrs., on salt-rising fermentation 48 

Roman bakers and dry yeast 16 

"Rope" in bread 4 1 

Royal Baking Powder Co 51, 67 

Rye, in aeration process 34 

in Vienna process 26 

in yeast mash 14 

Saccharomyces cerevisae I, 3 

Saleratus (see sodium bicarbonate) 53 

Salt-rising bacteria, characteristics 50 

in cornmeal and flour 48 

experiments of Kohman 49 

in the air 48 

isolation 49 

products of fermentation 49 

Salt-rising bread, "emptyings" 50 

flavor and structure 48 

loss in fermentation 49 

recipe for 50 

Salt-rising fermentation, enzymic theory 47 

function of salt in 47 

milk in 47 

products 49 

"S. A. S." (see basic sodic aluminic sulfate). 

"Sauerteig" 48 

Schwann, vegetable nature of yeast I 

Scotch bakers 36 

Secondary fermentation 16 

Self -rising flour 63 

Separator for yeast manufacture 33 

Slop, from yeast manufacture 31 

Soda (see sodium bicarbonate) 53 

Sodium bicarbonate, addition to baking powder 61 

in baking powder formula 52, 53 

drying 63 

in leading baking powders 59 

residue in bread 53, 61 

substitute for baking powder 61 

Sodium sulfate, in baking powder formula 57 

source of 56 



Solvay process 53 

Sour milk, in baking powder 61 

Sponge dough 36 

Stahl, theory of fermentation 2 

Starch, determination 65 

in leading baking powders 59 

moisture in 58, 63 

symbol and qualities 1 1 

in yeast 17, 33 

as yeast food 8 

in yeast mash 26 

Straight dough 36, 43 

Succinic acid 7 

from fermentation 10 

flavor of bread 41 

in yeast excretions 3, 7 

Sugars, in barley and malt 10 

fermentable, as yeast foods , 8 

relation to fermentation 8-15 

Tartaric acid, aerating value 55, 58 

determination 65 

in baking powder 55, 63 

in leading baking powders 59 

manufacture 54 

Tests, for baking powder , 64, 65 

yeast 20 

Theories of fermentation 2, 47 

Top yeasts, analysis 3, 7 

Traube, on enzymes . . . 2 

Tyrosin, flavor of bread 41 

isolated by Ehrlich 10 

Vienna process 22, 25-33 

diagram of 23 

Voorhees, loss of bread substance '. 42 

Water, in baking powder formula 52 

in barley and malt 10 

in baking powders 59 

in Pasteur's experiment 8 

in yeast 6 

Whiting, Dr., formula for baking powder 63 

Whole-wheat flour 63 



Wild yeasts 3, 15 

Withington, Mr., and aerated bread 70 

Wort, defined 10 

difference between distiller's and yeastmaker's. 9 

in aeration process 34 

Wright, Luke, aerated bread patent 69 

Yeast, amount in bread 4 1 

analysis, of dry matter 6 

organic constituents 7 

ash 7 

excretions 7 

auto-fermentation 6 

in bread 36 

breathing . 8 

cell 6 

cellulose in dry matter 6 

compressed manufacture 21-40 

dies in dough 43 

effect of lactic acid on 6 

electric current . .'.' 4 

fermentation 8 

flavor in bread 38 

foods 8 

great pressure 4 

growth in dough 42 

home-made 43-46 

keeping of by bakers 17 

killed by heat 4 

long-distance shipments 17-20 

manufacture, diagrams of 12, 13 

drying and pressing 31 

lactic acid in 26 

skimming 29 

slop 31 

washing 29 

mash 14, 22 

normal moisture 4 

nutrition 8 

percentage of water in 6 

in plaster of paris 5 

pure culture 16 

and "ropy bread" 41 



Yeast continued PAGE 

rye 20 

sensitive to acids 6 

spores 5 

starch in 17 

taste and odor 20 

temperature of reproduction and fermentation 4 

tests for 20 

wheat 20 

yield in manufacture 25 

Zymase, discovered by Buchner 2 

properties 15 


ARNDT-KATZ A Popular Treatise on the Colloids in the Industrial 
Arts. Translated from the Second Enlarged German Edition. I2mo. 
Pages VI + 73 $0.75 

ARNOLD The Motor and the Dynamo. 8vo. Pages VI -f- 178. 

166 Figures $1.50 

BENEDICT Elementary Organic Analysis. Small 8vo. Pages VI -f 82 
15 Illustrations $i .00 

BERGEY Handbook of Practical Hygiene. Small 8vo. Pages 164.. $1.50 

BILTZ The Practical Methods of Determining Molecular Weights. 
(Translated by Jones). Small 8vo. Pages VIII + 245. 44 Illus- 
trations $2.00 

BOLTON History of the Thermometer. I2mo. Pages 96. 6 Illus- 
trations $T.OO 

BURGESS Soil Bacteriology Laboratory Manual. I2mo. Pages VIII + 
123. 3 Illustrations $1.00 

CAMERON The Soil Solution, or the Nutrient Medium for Plant Growth. 
8vo. Pages VI -f 136. 3 Illustrations $1.25 

COLBY Reinforced Concrete in Europe. 8vo. Pages X -f 260 $3.50 

EMERY Elementary Chemistry. 12010. Pages XIV -f 666. 191 Il- 
lustrations $1.50 

ENGELHARDT The Electrolysis of Water. 8vo. Pages X -f 140. 90 
Illustrations $1.25 

FR APS Principles of Agricultural Chemistry. 8vo. Pages VI -f 493. 
94 Illustrations $4.00 

GILMAN A Laboratory Outline for Determinations in Quantitative 
Chemical Analysis. Pages 88 $0.90 

GRAVES Mechanical Drawing. 8vo. Pages VI -f- *39- 98 Figures and 
Plates $2.00 

GRAVES Orthographic Projection. 8vo. Pages 89. 75 Figures. . .$1.50 

GUILD The Mineralogy of Arizona. Small I2mo. Pages 104. Il- 
lustrated $1.00 

HALLIGAN Elementary Treatise on Stock Feeds and Feeding. 8vo. 
Pages VI -f 302. 24 Figures $2.50 

HALLIGANFertility and Fertilizer Hints. 8vo. Pages VIII + 156. 12 
Figures $1.25 

HALLIGAN Soil Fertility and Fertilizers. 8vo. Pages X -j- 398. 2 6 
Figures $3.50 

HARDY Infinitesimals and Limits. Small I2mo. Paper. Pages 22. 
6 Figures $0.20 

HART Chemistry for Beginners. Small I2mo. Vol. I. Inorganic. Pages 
VIII -f 214. 55 Illustrations, 2 Plates $1.00 

HART Chemistry for Beginners. Small I2mo. Vol. II. Pages IV -f 
98. 1 1 Illustrations $0.50 

HART Second Year Chemistry. Small I2mo. Pages 165. 31 Illus- 
trations $1.25 

HART, R. N. Welding. 8vo. Pages XVI + 182. 93 Illustrations. $2.50 

HEESS Practical Methods for the Iron and Steel Works Chemist. 
Pages 60 $1.00 

HILL A Brief Laboratory Guide for Qualitative Analysis. I2mo. Pages 
VI + 80 $1.00 

HINDS Qualitative Chemical Analysis. 8vo. Pages VIII -f 266.. $2.00 

HOWE Inorganic Chemistry for Schools and Colleges. 8vo. Pages 
VIII +422 $3.00 

JONES The Freezing Point, Boiling Point and Conductivity Methods. 
Pages VIII -f- 76. 2nd Edition, completely revised $1.00 

KRAYER The Use and Care of a Balance. Small I2mo. Pages IV -f 
42. 18 Illustrations $0.75 

LANDOLT The Optical Rotating Power of Organic Substances and Its 
Practical Applications. 8vo. Pages XXI + 751. 83 Illustra- 
tions $7-50 

LEA VENWORTH Inorganic Qualitative Chemical Analysis. 8vo. Pages 
VI -f 153 $i-5o 

LE BLANC The Production of Chromium and Its Compounds by the Aid 
of the Electric Current. 8vo. Pages 122 $1.25 

MASON Notes on Qualitative Analysis. Small I2mo. Pages 56 ... .$0.80 

MEADE Chemists' Pocket Manual. I2mo. Pages XII + 444. 30 
Illustrations $3-OO 

MEADE Portland Cement. 2nd Edition. 8vo. Pages X -f 512. 169 
Illustrations $4-5o 

MOELLER-KRAUSE Practical Handbook for Beet-Sugar Chemists. 8vo. 
Pages VIII -f 132. 19 Illustrations $1.25 

MOISSAN The Electric Furnace. 8vo. Pages 10 -f 305. 41 Illus- 
trations $2-50 

NIKAIDO Beet-Sugar Making and Its Chemical Control. 8vo. Pages 
XII -f 354. 65 Illustrations $3.00 

NISSENSON The Arrangement of Electrolytic Laboratories. 8vo. Pages 
81. 52 Illustrations $1.25 

NOYES Organic Chemistry for the Laboratory. 2d Edition, revised 
and enlarged. 8vo. Pages XII -f 292. 41 Illustrations $2.00 

NOYES AND MULLIKEN Laboratory Experiments on Class Reactions 
and Identification of Organic Substances. 8vo. Pages 81 $0.50 

PARSONS The Chemistry and Literature of Beryllium. 8vo. Pages 
VI + 180 $2.00 

PFANHAUSER Production of Metallic Objects Electrolytically. 8vo. 
Pages 162. 100 Illustrations $1.25 

PHILLIPS Chemical German. 8vo. Pages XII + 241 $2.00 

PHILLIPS Methods for the Analysis of Ores, Pig Iron and Steel. 2nd 
Edition. 8vo. Pages VIII -f 170. 3 Illustrations $1.00 

PRANKE Cyanamid (Manufacture, Chemistry and Uses). 8vo. Pages 
VI + 112. 8 Figures $1.25 

SEGER Collected Writings of Herman August Seger. Papers on Manu- 
facture of Pottery. 2 Vols. Large 8vo $7.50 a vol. or $15.00 a set 

STILLMAN Engineering Chemistry. 4th Edition. 8vo. Pages X -f 
744. 174 Illustrations $5.00 

STILLMAN Examination of Lubricating Oils. 8vo. Pages IV -f- 125. 
35 Illustrations $1.25 

TOWER The Conductivity of Liquids. 8vo. Pages 82. 20 Illus- 
trations $1-50 

VENABLE The Development of the Periodic Law. Small I2mo. Pages 
VIII -f 321. Illustrated $2.50 

VENABLE The Study of the Atom. I2mo. Pages VI -f 290 $2.00 

VULTE AND GOODELL Household Chemistry. 2nd Edition. I2mo 

Pages VI -f 190 $1.25 

VULTE AND VANDERBILT Food Industries An Elementary Text-book 
on the Production and Manufacture of Staple Foods. 8vo. Pages 
X + 310. 78 Illustrations $i.7S 

WILEY Principles and Practice of Agricultural Chemical Analysis. Vol. 

I. Soils. Pages XII -f 636. 55 Illustrations. 17 Plates $4.00 

WILEY Principles and Practice of Agricultural Chemical Analysis. Vol. 

II. Fertilizers and Insecticides. Pages 684. 40 Illustrations. 7 
Plates $4-50 

WILEY Principles and Practice of Agricultural Analysis. Vol. III. 
Agricultural Products. Pages XVI -f 846. 127 Illustrations $6.00 

WYSOR Analysis of Metallurgical and Engineering Materials, a Sys- 
tematic Arrangement of Laboratory Methods. Size 8 l / 2 x io l / 2 . Pages 
82. Illustrated. Blank Pages for Notes $2.00 

WYSOR Metallurgy a Condensed Treatise for the Use of College 
Students and Any Desiring a General Knowledge of the Subject. 
Second Edition, revised and enlarged. 8vo. Pages XIV + 391- 
104 Illustrations $3-00 

RETURN TO the circulation desk of any 
University of California Library 
or to the 

Bldg. 400, Richmond Field Station 
University of California 
Richmond, CA 94804-4698 

2-month loans may be renewed by calling 

(415) 642-6753 
1-year loans may be recharged by bringing books 

to NRLF 
Renewals and recharges may be made 4 days 

prior to due date 


APR t t J99J 



MAY 2 6 2000 





J 32^570^ : :